diff --git a/accessible/aom/AccessibleNode.h b/accessible/aom/AccessibleNode.h
index e9fd4d4bb009..d94703b6dbe1 100644
--- a/accessible/aom/AccessibleNode.h
+++ b/accessible/aom/AccessibleNode.h
@@ -10,7 +10,6 @@
 #include "nsDataHashtable.h"
 #include "nsRefPtrHashtable.h"
 #include "nsWrapperCache.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/DOMString.h"
 #include "mozilla/dom/Nullable.h"
@@ -19,6 +18,8 @@ class nsINode;
 
 namespace mozilla {
 
+class ErrorResult;
+
 namespace a11y {
 class Accessible;
 }
diff --git a/devtools/shared/heapsnapshot/DominatorTree.h b/devtools/shared/heapsnapshot/DominatorTree.h
index dd88f1d08e22..e8e06ee076a1 100644
--- a/devtools/shared/heapsnapshot/DominatorTree.h
+++ b/devtools/shared/heapsnapshot/DominatorTree.h
@@ -8,12 +8,13 @@
 
 #include "mozilla/devtools/HeapSnapshot.h"
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefCounted.h"
 #include "js/UbiNodeDominatorTree.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace devtools {
 
 class DominatorTree final : public nsISupports, public nsWrapperCache {
diff --git a/devtools/shared/heapsnapshot/HeapSnapshot.h b/devtools/shared/heapsnapshot/HeapSnapshot.h
index 5f54a6ea8d3a..b4aa316f4cee 100644
--- a/devtools/shared/heapsnapshot/HeapSnapshot.h
+++ b/devtools/shared/heapsnapshot/HeapSnapshot.h
@@ -7,7 +7,6 @@
 #define mozilla_devtools_HeapSnapshot__
 
 #include "js/HashTable.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/devtools/DeserializedNode.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/Nullable.h"
@@ -27,6 +26,8 @@
 #include "nsXPCOM.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace devtools {
 
 class DominatorTree;
diff --git a/docshell/base/BrowsingContext.h b/docshell/base/BrowsingContext.h
index a5c28da8f797..2abae03069b2 100644
--- a/docshell/base/BrowsingContext.h
+++ b/docshell/base/BrowsingContext.h
@@ -15,7 +15,6 @@
 #include "mozilla/RefPtr.h"
 #include "mozilla/Span.h"
 #include "mozilla/Tuple.h"
-#include "mozilla/WeakPtr.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/FeaturePolicy.h"
 #include "mozilla/dom/LocationBase.h"
diff --git a/docshell/base/SyncedContext.h b/docshell/base/SyncedContext.h
index 56dd7d958f8d..e9ad5017cf1d 100644
--- a/docshell/base/SyncedContext.h
+++ b/docshell/base/SyncedContext.h
@@ -7,12 +7,16 @@
 #ifndef mozilla_dom_SyncedContext_h
 #define mozilla_dom_SyncedContext_h
 
-#include "mozilla/EnumSet.h"
-#include "mozilla/ErrorResult.h"
-#include "mozilla/Maybe.h"
-#include "mozilla/RefPtr.h"
-#include "mozilla/Tuple.h"
+#include <array>
+#include <type_traits>
 #include <utility>
+#include "mozilla/Attributes.h"
+#include "mozilla/EnumSet.h"
+#include "nsStringFwd.h"
+#include "nscore.h"
+
+// Referenced via macro definitions
+#include "mozilla/ErrorResult.h"
 
 class PickleIterator;
 
@@ -31,6 +35,8 @@ struct IPDLParamTraits;
 namespace dom {
 class ContentParent;
 class ContentChild;
+template <typename T>
+class MaybeDiscarded;
 
 namespace syncedcontext {
 
diff --git a/docshell/base/WindowContext.h b/docshell/base/WindowContext.h
index 6ff4e9eb4f60..748f284b9fa5 100644
--- a/docshell/base/WindowContext.h
+++ b/docshell/base/WindowContext.h
@@ -9,7 +9,6 @@
 
 #include "mozilla/PermissionDelegateHandler.h"
 #include "mozilla/Span.h"
-#include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/MaybeDiscarded.h"
 #include "mozilla/dom/SyncedContext.h"
 #include "mozilla/dom/UserActivation.h"
@@ -27,6 +26,7 @@ namespace dom {
 
 class WindowGlobalParent;
 class WindowGlobalInit;
+class BrowsingContext;
 class BrowsingContextGroup;
 
 #define MOZ_EACH_WC_FIELD(FIELD)                                       \
diff --git a/docshell/base/nsILoadContext.idl b/docshell/base/nsILoadContext.idl
index 234ba531c2b4..af71b96b347d 100644
--- a/docshell/base/nsILoadContext.idl
+++ b/docshell/base/nsILoadContext.idl
@@ -14,7 +14,9 @@ webidl Element;
 
 %{C++
 #ifdef MOZILLA_INTERNAL_API
-#include "mozilla/BasePrincipal.h" // for OriginAttributes
+namespace mozilla {
+class OriginAttributes;
+}
 #endif
 %}
 
diff --git a/docshell/shistory/ChildSHistory.h b/docshell/shistory/ChildSHistory.h
index 9dbba23ad59c..43b2f63bd03b 100644
--- a/docshell/shistory/ChildSHistory.h
+++ b/docshell/shistory/ChildSHistory.h
@@ -21,9 +21,9 @@
 
 #include "nsCOMPtr.h"
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 #include "nsThreadUtils.h"
+#include "mozilla/ErrorResult.h"
 #include "mozilla/LinkedList.h"
 #include "nsID.h"
 
diff --git a/dom/abort/AbortController.h b/dom/abort/AbortController.h
index f2e31c372805..c653f2a768b5 100644
--- a/dom/abort/AbortController.h
+++ b/dom/abort/AbortController.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_AbortController_h
 
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
@@ -16,6 +15,8 @@
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class AbortSignal;
diff --git a/dom/animation/CSSPseudoElement.h b/dom/animation/CSSPseudoElement.h
index 0a195bec1e36..fbc02939ce4f 100644
--- a/dom/animation/CSSPseudoElement.h
+++ b/dom/animation/CSSPseudoElement.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/RefPtr.h"
 #include "nsCSSPseudoElements.h"
diff --git a/dom/base/BodyConsumer.h b/dom/base/BodyConsumer.h
index f75b33d5b992..2a7ab4af02f0 100644
--- a/dom/base/BodyConsumer.h
+++ b/dom/base/BodyConsumer.h
@@ -10,7 +10,6 @@
 #include "mozilla/dom/AbortSignal.h"
 #include "mozilla/dom/MutableBlobStorage.h"
 #include "nsIInputStreamPump.h"
-#include "nsNetUtil.h"
 #include "nsIObserver.h"
 #include "nsWeakReference.h"
 
diff --git a/dom/base/BodyStream.h b/dom/base/BodyStream.h
index b16d49631e45..33b1166006d8 100644
--- a/dom/base/BodyStream.h
+++ b/dom/base/BodyStream.h
@@ -15,7 +15,6 @@
 #include "nsISupportsImpl.h"
 #include "nsNetCID.h"
 #include "nsWeakReference.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Mutex.h"
 
 class nsIGlobalObject;
@@ -23,6 +22,8 @@ class nsIGlobalObject;
 class nsIInputStream;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BodyStream;
diff --git a/dom/base/BodyUtil.h b/dom/base/BodyUtil.h
index 3e56ad93a1a4..bed0eb1dbbbc 100644
--- a/dom/base/BodyUtil.h
+++ b/dom/base/BodyUtil.h
@@ -10,11 +10,12 @@
 #include "nsString.h"
 #include "nsError.h"
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/FormData.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BodyUtil final {
diff --git a/dom/base/ChromeUtils.cpp b/dom/base/ChromeUtils.cpp
index 88337c6ee246..746b94bd5145 100644
--- a/dom/base/ChromeUtils.cpp
+++ b/dom/base/ChromeUtils.cpp
@@ -13,28 +13,21 @@
 #include "WrapperFactory.h"
 
 #include "mozilla/Base64.h"
-#include "mozilla/BasePrincipal.h"
 #include "mozilla/CycleCollectedJSRuntime.h"
 #include "mozilla/IntentionalCrash.h"
 #include "mozilla/PerformanceMetricsCollector.h"
 #include "mozilla/PerfStats.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/ProcInfo.h"
-#include "mozilla/RDDProcessManager.h"
 #include "mozilla/ResultExtensions.h"
 #include "mozilla/SharedStyleSheetCache.h"
 #include "mozilla/TimeStamp.h"
-#include "mozilla/dom/BrowsingContext.h"
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/IdleDeadline.h"
 #include "mozilla/dom/InProcessParent.h"
-#include "mozilla/dom/InProcessChild.h"
 #include "mozilla/dom/JSActorService.h"
-#include "mozilla/dom/MediaMetadata.h"
 #include "mozilla/dom/MediaSessionBinding.h"
 #include "mozilla/dom/PBrowserParent.h"
-#include "mozilla/dom/PWindowGlobalParent.h"
 #include "mozilla/dom/Performance.h"
 #include "mozilla/dom/PopupBlocker.h"
 #include "mozilla/dom/Promise.h"
@@ -43,12 +36,9 @@
 #include "mozilla/dom/WindowBinding.h"  // For IdleRequestCallback/Options
 #include "mozilla/dom/WindowGlobalParent.h"
 #include "mozilla/dom/WorkerPrivate.h"
-#include "mozilla/gfx/GPUProcessManager.h"
 #include "mozilla/ipc/GeckoChildProcessHost.h"
 #include "mozilla/net/UrlClassifierFeatureFactory.h"
-#include "mozilla/net/SocketProcessHost.h"
 #include "IOActivityMonitor.h"
-#include "nsIOService.h"
 #include "nsThreadUtils.h"
 #include "mozJSComponentLoader.h"
 #include "GeckoProfiler.h"
diff --git a/dom/base/ChromeUtils.h b/dom/base/ChromeUtils.h
index d372031d58d6..974d1897a120 100644
--- a/dom/base/ChromeUtils.h
+++ b/dom/base/ChromeUtils.h
@@ -11,13 +11,14 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/ChromeUtilsBinding.h"
 #include "mozilla/dom/Exceptions.h"
-#include "mozilla/ErrorResult.h"
 #include "nsDOMNavigationTiming.h"  // for DOMHighResTimeStamp
 #include "nsIDOMProcessChild.h"
 #include "nsIDOMProcessParent.h"
 
 namespace mozilla {
 
+class ErrorResult;
+
 namespace devtools {
 class HeapSnapshot;
 }  // namespace devtools
diff --git a/dom/base/Crypto.cpp b/dom/base/Crypto.cpp
index ec3fc6b0ebd1..2b8bfbbe70e1 100644
--- a/dom/base/Crypto.cpp
+++ b/dom/base/Crypto.cpp
@@ -4,19 +4,15 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "Crypto.h"
-#include "jsfriendapi.h"
+#include "js/ScalarType.h"
 #include "js/experimental/TypedData.h"  // JS_GetArrayBufferViewType
 #include "nsCOMPtr.h"
 #include "nsIRandomGenerator.h"
-#include "MainThreadUtils.h"
-#include "nsXULAppAPI.h"
 
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/CryptoBinding.h"
+#include "mozilla/dom/SubtleCrypto.h"
 #include "nsServiceManagerUtils.h"
 
-using mozilla::dom::ContentChild;
-
 namespace mozilla::dom {
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(Crypto)
diff --git a/dom/base/CustomElementRegistry.h b/dom/base/CustomElementRegistry.h
index a95d395e9407..14437a6961ba 100644
--- a/dom/base/CustomElementRegistry.h
+++ b/dom/base/CustomElementRegistry.h
@@ -11,7 +11,6 @@
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/CycleCollectedJSContext.h"  // for MicroTaskRunnable
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/CustomElementRegistryBinding.h"
 #include "mozilla/dom/Document.h"
@@ -23,6 +22,8 @@
 #include "nsContentUtils.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct CustomElementData;
diff --git a/dom/base/DOMImplementation.h b/dom/base/DOMImplementation.h
index 68f8046997a7..d33f54b82960 100644
--- a/dom/base/DOMImplementation.h
+++ b/dom/base/DOMImplementation.h
@@ -10,7 +10,6 @@
 #include "nsWrapperCache.h"
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsIScriptGlobalObject.h"
@@ -19,6 +18,8 @@
 #include "nsString.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 class Document;
 class DocumentType;
diff --git a/dom/base/DOMParser.h b/dom/base/DOMParser.h
index 697b80bb7905..cd59b4c4b39c 100644
--- a/dom/base/DOMParser.h
+++ b/dom/base/DOMParser.h
@@ -10,7 +10,6 @@
 #include "nsCOMPtr.h"
 #include "mozilla/dom/Document.h"
 #include "nsWrapperCache.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Span.h"
 #include "mozilla/dom/DOMParserBinding.h"
 #include "mozilla/dom/TypedArray.h"
@@ -18,6 +17,8 @@
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class DOMParser final : public nsISupports, public nsWrapperCache {
diff --git a/dom/base/FormData.h b/dom/base/FormData.h
index 2bbad1b0cf92..492b134a9026 100644
--- a/dom/base/FormData.h
+++ b/dom/base/FormData.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_FormData_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/HTMLFormSubmission.h"
 #include "mozilla/dom/File.h"
@@ -17,6 +16,8 @@
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class HTMLFormElement;
diff --git a/dom/base/IdleDeadline.h b/dom/base/IdleDeadline.h
index 9df3440fc312..10f149e63cd5 100644
--- a/dom/base/IdleDeadline.h
+++ b/dom/base/IdleDeadline.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "nsCOMPtr.h"
diff --git a/dom/base/Location.h b/dom/base/Location.h
index c6e7ae4ef5f6..ce472b318d04 100644
--- a/dom/base/Location.h
+++ b/dom/base/Location.h
@@ -12,14 +12,13 @@
 #include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/LocationBase.h"
 #include "nsCycleCollectionParticipant.h"
-#include "nsIWeakReferenceUtils.h"
-#include "nsPIDOMWindow.h"
 #include "nsString.h"
 #include "nsWrapperCache.h"
 
 class nsIDocShell;
+class nsIPrincipal;
 class nsIURI;
-class nsDocShellLoadState;
+class nsPIDOMWindowInner;
 
 namespace mozilla {
 namespace dom {
diff --git a/dom/base/LocationBase.h b/dom/base/LocationBase.h
index 1dec70130939..c0c57bb1da51 100644
--- a/dom/base/LocationBase.h
+++ b/dom/base/LocationBase.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_LocationBase_h
 
 #include "mozilla/AlreadyAddRefed.h"
-#include "mozilla/ErrorResult.h"
 #include "nsStringFwd.h"
 
 class nsIDocShell;
@@ -17,6 +16,8 @@ class nsIURI;
 class nsDocShellLoadState;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 class BrowsingContext;
 
diff --git a/dom/base/MozQueryInterface.h b/dom/base/MozQueryInterface.h
index 1d19f4504a07..1dd3d9bfff6e 100644
--- a/dom/base/MozQueryInterface.h
+++ b/dom/base/MozQueryInterface.h
@@ -21,10 +21,11 @@
 
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/NonRefcountedDOMObject.h"
-#include "mozilla/ErrorResult.h"
 #include "nsID.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class MozQueryInterface final : public NonRefcountedDOMObject {
diff --git a/dom/base/Navigator.h b/dom/base/Navigator.h
index 043fa07e152c..99be251bf05a 100644
--- a/dom/base/Navigator.h
+++ b/dom/base/Navigator.h
@@ -12,7 +12,6 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/Fetch.h"
 #include "mozilla/dom/Nullable.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 #include "nsHashKeys.h"
 #include "nsInterfaceHashtable.h"
@@ -28,6 +27,8 @@ class nsIPrincipal;
 class nsIURI;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 class AddonManager;
 class BodyExtractorBase;
diff --git a/dom/base/PlacesEvent.h b/dom/base/PlacesEvent.h
index 46ac66460492..74c36e158fa8 100644
--- a/dom/base/PlacesEvent.h
+++ b/dom/base/PlacesEvent.h
@@ -8,10 +8,11 @@
 #define mozilla_dom_PlacesEvent_h
 
 #include "mozilla/dom/PlacesEventBinding.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class PlacesEvent : public nsWrapperCache {
diff --git a/dom/base/PlacesObservers.h b/dom/base/PlacesObservers.h
index 33de57ada64e..516aebc42162 100644
--- a/dom/base/PlacesObservers.h
+++ b/dom/base/PlacesObservers.h
@@ -11,11 +11,11 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/PlacesObserversBinding.h"
 #include "mozilla/dom/PlacesEvent.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/places/INativePlacesEventCallback.h"
 #include "nsIWeakReferenceUtils.h"
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 
diff --git a/dom/base/PlacesWeakCallbackWrapper.h b/dom/base/PlacesWeakCallbackWrapper.h
index 74ff59067304..c7ed3aa42989 100644
--- a/dom/base/PlacesWeakCallbackWrapper.h
+++ b/dom/base/PlacesWeakCallbackWrapper.h
@@ -9,7 +9,6 @@
 
 #include "mozilla/WeakPtr.h"
 #include "mozilla/dom/PlacesObserversBinding.h"
-#include "mozilla/ErrorResult.h"
 #include "nsIWeakReferenceUtils.h"
 #include "nsWrapperCache.h"
 
diff --git a/dom/base/PopupBlocker.h b/dom/base/PopupBlocker.h
index d6e82151f6c0..b71ff5995f9a 100644
--- a/dom/base/PopupBlocker.h
+++ b/dom/base/PopupBlocker.h
@@ -7,12 +7,17 @@
 #ifndef mozilla_dom_PopupBlocker_h
 #define mozilla_dom_PopupBlocker_h
 
-#include "mozilla/BasicEvents.h"
+#include <stdint.h>
+#include "mozilla/Attributes.h"
+#include "mozilla/TimeStamp.h"
 
+class AutoPopupStatePusherInternal;
 class nsIPrincipal;
 
 namespace mozilla {
+class WidgetEvent;
 namespace dom {
+class Event;
 
 class PopupBlocker final {
  public:
diff --git a/dom/base/Pose.h b/dom/base/Pose.h
index 1373eeb06154..4ca5df1e082e 100644
--- a/dom/base/Pose.h
+++ b/dom/base/Pose.h
@@ -7,10 +7,11 @@
 #ifndef mozilla_dom_Pose_h
 #define mozilla_dom_Pose_h
 
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Pose : public nsWrapperCache {
diff --git a/dom/base/ResizeObserver.h b/dom/base/ResizeObserver.h
index b3a79e016a86..83843b8cf4a8 100644
--- a/dom/base/ResizeObserver.h
+++ b/dom/base/ResizeObserver.h
@@ -10,7 +10,6 @@
 #include "js/TypeDecls.h"
 #include "mozilla/AppUnits.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/WritingModes.h"
 #include "mozilla/dom/DOMRect.h"
@@ -26,6 +25,8 @@
 #include "nsPIDOMWindow.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Element;
diff --git a/dom/base/StaticRange.h b/dom/base/StaticRange.h
index 6b2669f5e10b..6e8ed1d0d333 100644
--- a/dom/base/StaticRange.h
+++ b/dom/base/StaticRange.h
@@ -7,7 +7,6 @@
 #ifndef mozilla_dom_StaticRange_h
 #define mozilla_dom_StaticRange_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RangeBoundary.h"
 #include "mozilla/dom/AbstractRange.h"
 #include "mozilla/dom/StaticRangeBinding.h"
@@ -15,6 +14,8 @@
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class StaticRange final : public AbstractRange {
diff --git a/dom/base/StructuredCloneBlob.h b/dom/base/StructuredCloneBlob.h
index 45e49f894694..8fc2c00cd999 100644
--- a/dom/base/StructuredCloneBlob.h
+++ b/dom/base/StructuredCloneBlob.h
@@ -7,19 +7,25 @@
 #ifndef mozilla_dom_StructuredCloneBlob_h
 #define mozilla_dom_StructuredCloneBlob_h
 
-#include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/dom/StructuredCloneHolder.h"
-#include "mozilla/dom/StructuredCloneHolderBinding.h"
-
-#include "jsapi.h"
-
+#include "js/TypeDecls.h"
+#include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/StructuredCloneHolder.h"
 #include "nsIMemoryReporter.h"
 #include "nsISupports.h"
 
+struct JSStructuredCloneReader;
+struct JSStructuredCloneWriter;
+
 namespace mozilla {
+
+class ErrorResult;
+
 namespace dom {
 
+class GlobalObject;
+
 class StructuredCloneBlob final : public nsIMemoryReporter {
   MOZ_DEFINE_MALLOC_SIZE_OF(MallocSizeOf)
 
diff --git a/dom/base/Text.h b/dom/base/Text.h
index a660e6043736..99a64dba2a69 100644
--- a/dom/base/Text.h
+++ b/dom/base/Text.h
@@ -8,9 +8,10 @@
 #define mozilla_dom_Text_h
 
 #include "mozilla/dom/CharacterData.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Text : public CharacterData {
diff --git a/dom/base/nsDOMAttributeMap.h b/dom/base/nsDOMAttributeMap.h
index c7066f25bc2e..c30b0898aed5 100644
--- a/dom/base/nsDOMAttributeMap.h
+++ b/dom/base/nsDOMAttributeMap.h
@@ -12,7 +12,6 @@
 #define nsDOMAttributeMap_h
 
 #include "mozilla/MemoryReporting.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsRefPtrHashtable.h"
 #include "nsString.h"
@@ -22,6 +21,8 @@ class nsAtom;
 class nsINode;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 class Attr;
 class DocGroup;
diff --git a/dom/base/nsDOMSerializer.h b/dom/base/nsDOMSerializer.h
index 3b48ced6fe8d..cebf3d9aaa21 100644
--- a/dom/base/nsDOMSerializer.h
+++ b/dom/base/nsDOMSerializer.h
@@ -8,12 +8,15 @@
 #define nsDOMSerializer_h_
 
 #include "mozilla/dom/NonRefcountedDOMObject.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/XMLSerializerBinding.h"
 
 class nsINode;
 class nsIOutputStream;
 
+namespace mozilla {
+class ErrorResult;
+}
+
 class nsDOMSerializer final : public mozilla::dom::NonRefcountedDOMObject {
  public:
   nsDOMSerializer();
diff --git a/dom/base/nsFocusManager.h b/dom/base/nsFocusManager.h
index dc817cd55af5..4b276d57b0ab 100644
--- a/dom/base/nsFocusManager.h
+++ b/dom/base/nsFocusManager.h
@@ -12,7 +12,6 @@
 #include "mozilla/dom/Document.h"
 #include "nsIFocusManager.h"
 #include "nsIObserver.h"
-#include "nsIWidget.h"
 #include "nsWeakReference.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/RefPtr.h"
diff --git a/dom/base/nsGlobalWindowInner.cpp b/dom/base/nsGlobalWindowInner.cpp
index 48ae9b65f897..1244e1adad2a 100644
--- a/dom/base/nsGlobalWindowInner.cpp
+++ b/dom/base/nsGlobalWindowInner.cpp
@@ -4,169 +4,304 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "nsGlobalWindow.h"
+#include "nsGlobalWindowInner.h"
 
-#include <algorithm>
-
-#include "mozilla/MemoryReporting.h"
-
-// Local Includes
+#include <inttypes.h>
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <cstdint>
+#include <new>
+#include <type_traits>
+#include <utility>
+#include "AudioChannelService.h"
 #include "AutoplayPolicy.h"
+#include "Crypto.h"
+#include "GeckoProfiler.h"
+#include "MainThreadUtils.h"
 #include "Navigator.h"
-#include "nsContentSecurityManager.h"
-#include "nsScreen.h"
-#include "nsHistory.h"
-#include "nsDOMNavigationTiming.h"
-#include "nsIDOMStorageManager.h"
+#include "PaintWorkletImpl.h"
+#include "SessionStorageCache.h"
+#include "Units.h"
+#include "VRManagerChild.h"
+#include "WindowDestroyedEvent.h"
+#include "WindowNamedPropertiesHandler.h"
+#include "js/ComparisonOperators.h"
+#include "js/CompileOptions.h"
+#include "js/Id.h"
+#include "js/PropertyDescriptor.h"
+#include "js/RealmOptions.h"
+#include "js/RootingAPI.h"
+#include "js/TypeDecls.h"
+#include "js/Value.h"
+#include "js/Warnings.h"
+#include "js/shadow/String.h"
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "mozIDOMWindow.h"
+#include "moz_external_vr.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/ArrayIterator.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BaseProfilerMarkersPrerequisites.h"
+#include "mozilla/BasicEvents.h"
+#include "mozilla/CallState.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/DOMEventTargetHelper.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/EventListenerManager.h"
+#include "mozilla/EventQueue.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/FlushType.h"
+#include "mozilla/Likely.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MacroForEach.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/OwningNonNull.h"
+#include "mozilla/PermissionDelegateHandler.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/ProcessHangMonitor.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Result.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/ScrollOrigin.h"
+#include "mozilla/ScrollTypes.h"
+#include "mozilla/Services.h"
+#include "mozilla/SizeOfState.h"
+#include "mozilla/Span.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StorageAccess.h"
+#include "mozilla/TaskCategory.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/TelemetryHistogramEnums.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/AudioContext.h"
+#include "mozilla/dom/BarProps.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/BrowserChild.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/CSPEvalChecker.h"
 #include "mozilla/dom/CallbackDebuggerNotification.h"
-#include "mozilla/dom/ContentChild.h"
+#include "mozilla/dom/ChromeMessageBroadcaster.h"
+#include "mozilla/dom/ClientInfo.h"
+#include "mozilla/dom/ClientManager.h"
+#include "mozilla/dom/ClientSource.h"
+#include "mozilla/dom/ClientState.h"
+#include "mozilla/dom/ClientsBinding.h"
+#include "mozilla/dom/Console.h"
 #include "mozilla/dom/ContentFrameMessageManager.h"
 #include "mozilla/dom/ContentMediaController.h"
-#include "mozilla/dom/ContentParent.h"
-#include "mozilla/dom/CSPEvalChecker.h"
 #include "mozilla/dom/CustomElementRegistry.h"
-#include "mozilla/dom/DebuggerNotification.h"
-#include "mozilla/dom/DocumentInlines.h"
 #include "mozilla/dom/DOMJSProxyHandler.h"
+#include "mozilla/dom/DebuggerNotification.h"
+#include "mozilla/dom/DebuggerNotificationBinding.h"
+#include "mozilla/dom/DebuggerNotificationManager.h"
+#include "mozilla/dom/DispatcherTrait.h"
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/Event.h"
 #include "mozilla/dom/EventTarget.h"
+#include "mozilla/dom/Fetch.h"
+#include "mozilla/dom/Gamepad.h"
+#include "mozilla/dom/GamepadManager.h"
+#include "mozilla/dom/HashChangeEvent.h"
+#include "mozilla/dom/HashChangeEventBinding.h"
+#include "mozilla/dom/IDBFactory.h"
+#include "mozilla/dom/IdleRequest.h"
+#include "mozilla/dom/ImageBitmap.h"
+#include "mozilla/dom/ImageBitmapSource.h"
+#include "mozilla/dom/InstallTriggerBinding.h"
+#include "mozilla/dom/IntlUtils.h"
+#include "mozilla/dom/LSObject.h"
+#include "mozilla/dom/LoadedScript.h"
 #include "mozilla/dom/LocalStorage.h"
 #include "mozilla/dom/LocalStorageCommon.h"
-#include "mozilla/dom/LSObject.h"
+#include "mozilla/dom/Location.h"
+#include "mozilla/dom/NavigatorBinding.h"
+#include "mozilla/dom/Nullable.h"
 #include "mozilla/dom/PartitionedLocalStorage.h"
-#include "mozilla/dom/Storage.h"
-#include "mozilla/dom/IdleRequest.h"
 #include "mozilla/dom/Performance.h"
+#include "mozilla/dom/PopStateEvent.h"
+#include "mozilla/dom/PopStateEventBinding.h"
+#include "mozilla/dom/PopupBlocker.h"
+#include "mozilla/dom/PrimitiveConversions.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/RootedDictionary.h"
 #include "mozilla/dom/ScriptLoader.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/ServiceWorker.h"
+#include "mozilla/dom/ServiceWorkerDescriptor.h"
+#include "mozilla/dom/ServiceWorkerRegistration.h"
 #include "mozilla/dom/SessionStorageManager.h"
+#include "mozilla/dom/SharedWorker.h"
+#include "mozilla/dom/Storage.h"
 #include "mozilla/dom/StorageEvent.h"
 #include "mozilla/dom/StorageEventBinding.h"
 #include "mozilla/dom/StorageNotifierService.h"
 #include "mozilla/dom/StorageUtils.h"
+#include "mozilla/dom/TabMessageTypes.h"
 #include "mozilla/dom/Timeout.h"
 #include "mozilla/dom/TimeoutHandler.h"
 #include "mozilla/dom/TimeoutManager.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/U2F.h"
+#include "mozilla/dom/VRDisplay.h"
+#include "mozilla/dom/VRDisplayEvent.h"
+#include "mozilla/dom/VRDisplayEventBinding.h"
+#include "mozilla/dom/VREventObserver.h"
 #include "mozilla/dom/VisualViewport.h"
-#include "mozilla/dom/WindowProxyHolder.h"
-#ifdef MOZ_GLEAN
-#  include "mozilla/glean/Glean.h"
-#endif
-#include "mozilla/IntegerPrintfMacros.h"
-#include "mozilla/Result.h"
-#if defined(MOZ_WIDGET_ANDROID)
-#  include "mozilla/dom/WindowOrientationObserver.h"
-#endif
-#include "nsDOMOfflineResourceList.h"
-#include "nsICookieService.h"
-#include "nsError.h"
-#include "nsISizeOfEventTarget.h"
-#include "nsDOMJSUtils.h"
-#include "nsArrayUtils.h"
 #include "mozilla/dom/WakeLock.h"
-#include "mozilla/dom/power/PowerManagerService.h"
+#include "mozilla/dom/WebIDLGlobalNameHash.h"
+#include "mozilla/dom/WindowBinding.h"
+#include "mozilla/dom/WindowContext.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "mozilla/dom/WorkerCommon.h"
+#include "mozilla/dom/Worklet.h"
+#include "mozilla/dom/XRPermissionRequest.h"
+#include "mozilla/dom/cache/CacheStorage.h"
+#include "mozilla/dom/cache/Types.h"
+#include "mozilla/fallible.h"
+#include "mozilla/gfx/BasePoint.h"
+#include "mozilla/gfx/BaseRect.h"
+#include "mozilla/gfx/BaseSize.h"
+#include "mozilla/gfx/Rect.h"
+#include "mozilla/gfx/Types.h"
+#include "mozilla/intl/LocaleService.h"
+#include "mozilla/net/CookieJarSettings.h"
+#include "nsAtom.h"
+#include "nsBaseHashtable.h"
+#include "nsCCUncollectableMarker.h"
+#include "nsCOMPtr.h"
+#include "nsCRT.h"
+#include "nsCRTGlue.h"
+#include "nsCanvasFrame.h"
+#include "nsCharTraits.h"
+#include "nsCheapSets.h"
+#include "nsContentUtils.h"
+#include "nsCoord.h"
+#include "nsCycleCollectionNoteChild.h"
+#include "nsCycleCollectionTraversalCallback.h"
+#include "nsDOMNavigationTiming.h"
+#include "nsDOMOfflineResourceList.h"
+#include "nsDebug.h"
+#include "nsDocShell.h"
+#include "nsFocusManager.h"
+#include "nsFrameMessageManager.h"
+#include "nsGkAtoms.h"
+#include "nsGlobalWindowOuter.h"
+#include "nsHashKeys.h"
+#include "nsHistory.h"
+#include "nsIAddonPolicyService.h"
+#include "nsIArray.h"
+#include "nsIBaseWindow.h"
+#include "nsIBrowserChild.h"
+#include "nsICancelableRunnable.h"
+#include "nsIChannel.h"
 #include "nsIContentSecurityPolicy.h"
+#include "nsIControllers.h"
+#include "nsICookieJarSettings.h"
+#include "nsICookieService.h"
+#include "nsID.h"
+#include "nsIDOMStorageManager.h"
+#include "nsIDeviceSensors.h"
+#include "nsIDocShell.h"
+#include "nsIDocShellTreeItem.h"
 #include "nsIDocShellTreeOwner.h"
 #include "nsIDocumentLoader.h"
-#include "nsIInterfaceRequestorUtils.h"
-#include "nsIScriptContext.h"
-#include "nsIController.h"
-#include "nsISlowScriptDebug.h"
-#include "nsWindowMemoryReporter.h"
-#include "nsWindowSizes.h"
-#include "WindowNamedPropertiesHandler.h"
-#include "nsFrameSelection.h"
-#include "nsNetUtil.h"
-#include "nsVariant.h"
-#include "nsPrintfCString.h"
-#include "mozilla/intl/LocaleService.h"
-#include "WindowDestroyedEvent.h"
-
-// Helper Classes
-#include "nsJSUtils.h"
-#include "jsapi.h"
-#include "jsfriendapi.h"
-#include "js/Warnings.h"  // JS::WarnASCII
-#include "js/Wrapper.h"
-#include "nsCharSeparatedTokenizer.h"
-#include "nsReadableUtils.h"
-#include "nsJSEnvironment.h"
-#include "mozilla/dom/ScriptSettings.h"
-#include "mozilla/Preferences.h"
-#include "mozilla/Likely.h"
-#include "mozilla/SpinEventLoopUntil.h"
-#include "mozilla/Sprintf.h"
-#include "mozilla/StorageAccess.h"
-#include "mozilla/Unused.h"
-
-// Other Classes
-#include "mozilla/dom/BarProps.h"
-#include "nsContentCID.h"
-#include "nsLayoutStatics.h"
-#include "nsCCUncollectableMarker.h"
-#include "mozilla/dom/WorkerCommon.h"
-#include "mozilla/dom/ToJSValue.h"
-#include "nsJSPrincipals.h"
-#include "mozilla/Attributes.h"
-#include "mozilla/Debug.h"
-#include "mozilla/EventListenerManager.h"
-#include "mozilla/EventStates.h"
-#include "mozilla/MouseEvents.h"
-#include "mozilla/PresShell.h"
-#include "mozilla/ProcessHangMonitor.h"
-#include "mozilla/ScrollTypes.h"
-#include "mozilla/ThrottledEventQueue.h"
-#include "AudioChannelService.h"
-#include "nsAboutProtocolUtils.h"
-#include "nsCharTraits.h"  // NS_IS_HIGH/LOW_SURROGATE
-#include "PostMessageEvent.h"
-#include "mozilla/dom/DocGroup.h"
-#include "mozilla/StaticPrefs_browser.h"
-#include "mozilla/StaticPrefs_dom.h"
-#include "PaintWorkletImpl.h"
-
-// Interfaces Needed
+#include "nsIDragService.h"
+#include "nsIFocusManager.h"
 #include "nsIFrame.h"
-#include "nsCanvasFrame.h"
+#include "nsIGlobalObject.h"
+#include "nsIIOService.h"
+#include "nsIIdleRunnable.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsILoadContext.h"
+#include "nsILoadGroup.h"
+#include "nsILoadInfo.h"
+#include "nsINamed.h"
+#include "nsINode.h"
+#include "nsIObserver.h"
+#include "nsIObserverService.h"
+#include "nsIPermission.h"
+#include "nsIPermissionManager.h"
+#include "nsIPrefBranch.h"
+#include "nsIPrincipal.h"
+#include "nsIPrompt.h"
+#include "nsIRunnable.h"
+#include "nsIScreen.h"
+#include "nsIScreenManager.h"
+#include "nsIScriptContext.h"
+#include "nsIScriptGlobalObject.h"
+#include "nsIScriptObjectPrincipal.h"
+#include "nsIScrollableFrame.h"
+#include "nsISerialEventTarget.h"
+#include "nsISimpleEnumerator.h"
+#include "nsISizeOfEventTarget.h"
+#include "nsISlowScriptDebug.h"
+#include "nsISupportsUtils.h"
+#include "nsIThread.h"
+#include "nsITimedChannel.h"
+#include "nsIURI.h"
+#include "nsIVariant.h"
+#include "nsIWeakReference.h"
+#include "nsIWebBrowserChrome.h"
+#include "nsIWebNavigation.h"
+#include "nsIWebProgressListener.h"
 #include "nsIWidget.h"
 #include "nsIWidgetListener.h"
-#include "nsIBaseWindow.h"
-#include "nsIDeviceSensors.h"
-#include "nsIContent.h"
-#include "nsIDocShell.h"
-#include "mozilla/dom/Document.h"
-#include "Crypto.h"
-#include "nsDOMString.h"
-#include "nsThreadUtils.h"
-#include "nsILoadContext.h"
-#include "nsIScrollableFrame.h"
-#include "nsView.h"
-#include "nsViewManager.h"
-#include "nsIPrompt.h"
-#include "nsIAddonPolicyService.h"
-#include "nsIWebNavigation.h"
-#include "nsIWebBrowserChrome.h"
-#include "nsDOMCID.h"
-#include "nsDOMWindowUtils.h"
-#include "nsIControllers.h"
-#include "nsGlobalWindowCommands.h"
+#include "nsJSPrincipals.h"
+#include "nsJSUtils.h"
+#include "nsLayoutStatics.h"
+#include "nsLiteralString.h"
+#include "nsNetUtil.h"
+#include "nsPIDOMWindow.h"
+#include "nsPIDOMWindowInlines.h"
+#include "nsPIWindowRoot.h"
+#include "nsPoint.h"
+#include "nsPresContext.h"
 #include "nsQueryObject.h"
-#include "nsContentUtils.h"
-#include "nsCSSProps.h"
-#include "mozilla/EventDispatcher.h"
-#include "mozilla/EventStateManager.h"
-#include "nsIObserverService.h"
-#include "nsFocusManager.h"
-#include "nsITimedChannel.h"
+#include "nsRefPtrHashtable.h"
+#include "nsSandboxFlags.h"
+#include "nsScreen.h"
 #include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "nsStringFlags.h"
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+#include "nsTLiteralString.h"
+#include "nsTObserverArray.h"
+#include "nsTStringRepr.h"
+#include "nsThreadUtils.h"
+#include "nsWeakReference.h"
+#include "nsWindowMemoryReporter.h"
+#include "nsWindowSizes.h"
+#include "nsWrapperCache.h"
+#include "nsWrapperCacheInlines.h"
+#include "nsXULAppAPI.h"
+#include "nsrootidl.h"
+#include "prclist.h"
+#include "prtypes.h"
+#include "xpcprivate.h"
+#include "xpcpublic.h"
+
 #ifdef MOZ_XUL
 #  include "nsIDOMXULControlElement.h"
 #  include "nsMenuPopupFrame.h"
 #endif
-#include "mozilla/dom/CustomEvent.h"
-#include "nsIScreenManager.h"
-#include "nsICSSDeclaration.h"
-#include "nsIPermission.h"
-
-#include "xpcprivate.h"
 
 #ifdef NS_PRINTING
 #  include "nsIPrintSettings.h"
@@ -174,72 +309,6 @@
 #  include "nsIWebBrowserPrint.h"
 #endif
 
-#include "nsWindowRoot.h"
-#include "nsNetCID.h"
-#include "nsIArray.h"
-
-#include "nsIDragService.h"
-#include "mozilla/dom/Element.h"
-#include "mozilla/dom/Selection.h"
-#include "nsFrameLoader.h"
-#include "nsXPCOMCID.h"
-#include "mozilla/Logging.h"
-#include "prenv.h"
-
-#include "mozilla/dom/IDBFactory.h"
-#include "mozilla/dom/MessageChannel.h"
-#include "mozilla/dom/Promise.h"
-
-#include "mozilla/dom/Gamepad.h"
-#include "mozilla/dom/GamepadManager.h"
-
-#include "gfxVR.h"
-#include "mozilla/dom/VRDisplay.h"
-#include "mozilla/dom/VRDisplayEvent.h"
-#include "mozilla/dom/VRDisplayEventBinding.h"
-#include "mozilla/dom/VREventObserver.h"
-#include "mozilla/dom/XRPermissionRequest.h"
-
-#include "nsRefreshDriver.h"
-#include "Layers.h"
-
-#include "mozilla/BasePrincipal.h"
-#include "mozilla/Services.h"
-#include "mozilla/Telemetry.h"
-#include "mozilla/dom/Location.h"
-#include "nsHTMLDocument.h"
-#include "nsWrapperCacheInlines.h"
-#include "mozilla/DOMEventTargetHelper.h"
-#include "prrng.h"
-#include "nsSandboxFlags.h"
-#include "mozilla/dom/AudioContext.h"
-#include "mozilla/dom/BrowserElementDictionariesBinding.h"
-#include "mozilla/dom/cache/CacheStorage.h"
-#include "mozilla/dom/Console.h"
-#include "mozilla/dom/Fetch.h"
-#include "mozilla/dom/FunctionBinding.h"
-#include "mozilla/dom/HashChangeEvent.h"
-#include "mozilla/dom/IntlUtils.h"
-#include "mozilla/dom/PopStateEvent.h"
-#include "mozilla/dom/PopupBlocker.h"
-#include "mozilla/dom/PopupBlockedEvent.h"
-#include "mozilla/dom/PrimitiveConversions.h"
-#include "mozilla/dom/WindowBinding.h"
-#include "nsIBrowserChild.h"
-#include "mozilla/dom/LoadedScript.h"
-#include "mozilla/dom/MediaQueryList.h"
-#include "mozilla/dom/ScriptSettings.h"
-#include "mozilla/dom/NavigatorBinding.h"
-#include "mozilla/dom/ImageBitmap.h"
-#include "mozilla/dom/ImageBitmapBinding.h"
-#include "mozilla/dom/InstallTriggerBinding.h"
-#include "mozilla/dom/SharedWorker.h"
-#include "mozilla/dom/ServiceWorker.h"
-#include "mozilla/dom/ServiceWorkerRegistration.h"
-#include "mozilla/dom/ServiceWorkerRegistrationDescriptor.h"
-#include "mozilla/dom/U2F.h"
-#include "mozilla/dom/WebIDLGlobalNameHash.h"
-#include "mozilla/dom/Worklet.h"
 #ifdef HAVE_SIDEBAR
 #  include "mozilla/dom/ExternalBinding.h"
 #endif
@@ -248,23 +317,16 @@
 #  include "mozilla/dom/SpeechSynthesis.h"
 #endif
 
-#include "mozilla/dom/ClientManager.h"
-#include "mozilla/dom/ClientSource.h"
-#include "mozilla/dom/ClientState.h"
-
-#include "mozilla/dom/WindowGlobalChild.h"
-#include "mozilla/dom/BrowserChild.h"
-
-#include "mozilla/net/CookieJarSettings.h"
-
-#include "AccessCheck.h"
-#include "SessionStorageCache.h"
-
 #ifdef ANDROID
 #  include <android/log.h>
 #endif
 
+#ifdef MOZ_WIDGET_ANDROID
+#  include "mozilla/dom/WindowOrientationObserver.h"
+#endif
+
 #ifdef XP_WIN
+#  include "mozilla/Debug.h"
 #  include <process.h>
 #  define getpid _getpid
 #else
diff --git a/dom/base/nsGlobalWindowInner.h b/dom/base/nsGlobalWindowInner.h
index 01e7f7b90efe..1ca89bddde98 100644
--- a/dom/base/nsGlobalWindowInner.h
+++ b/dom/base/nsGlobalWindowInner.h
@@ -41,7 +41,6 @@
 #include "mozilla/dom/StorageEventBinding.h"
 #include "mozilla/dom/UnionTypes.h"
 #include "mozilla/CallState.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/OwningNonNull.h"
@@ -98,6 +97,8 @@ class PromiseDocumentFlushedResolver;
 
 namespace mozilla {
 class AbstractThread;
+class ErrorResult;
+
 namespace dom {
 class BarProp;
 class BrowsingContext;
diff --git a/dom/base/nsGlobalWindowOuter.h b/dom/base/nsGlobalWindowOuter.h
index 17eede45a1cc..10c915229479 100644
--- a/dom/base/nsGlobalWindowOuter.h
+++ b/dom/base/nsGlobalWindowOuter.h
@@ -39,7 +39,6 @@
 #include "mozilla/dom/StorageEvent.h"
 #include "mozilla/dom/StorageEventBinding.h"
 #include "mozilla/dom/UnionTypes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/LinkedList.h"
 #include "nsWrapperCacheInlines.h"
@@ -84,6 +83,7 @@ class nsWindowSizes;
 namespace mozilla {
 class AbstractThread;
 class DOMEventTargetHelper;
+class ErrorResult;
 class ThrottledEventQueue;
 namespace dom {
 class BarProp;
diff --git a/dom/base/nsHistory.h b/dom/base/nsHistory.h
index 0f96a4a8cc30..2ee68df727e3 100644
--- a/dom/base/nsHistory.h
+++ b/dom/base/nsHistory.h
@@ -7,7 +7,6 @@
 #define nsHistory_h___
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/HistoryBinding.h"
 #include "mozilla/dom/ChildSHistory.h"
 #include "nsCOMPtr.h"
@@ -22,6 +21,10 @@ class nsISHistory;
 class nsIWeakReference;
 class nsPIDOMWindowInner;
 
+namespace mozilla {
+class ErrorResult;
+}
+
 // Script "History" object
 class nsHistory final : public nsISupports, public nsWrapperCache {
  public:
diff --git a/dom/base/nsIDocumentObserver.h b/dom/base/nsIDocumentObserver.h
index f278b3c13d20..6bf08fce9146 100644
--- a/dom/base/nsIDocumentObserver.h
+++ b/dom/base/nsIDocumentObserver.h
@@ -6,13 +6,13 @@
 #ifndef nsIDocumentObserver_h___
 #define nsIDocumentObserver_h___
 
-#include "mozilla/EventStates.h"
-#include "mozilla/StyleSheet.h"
 #include "nsISupports.h"
 #include "nsIMutationObserver.h"
 
 class nsIContent;
 namespace mozilla {
+class EventStates;
+
 namespace dom {
 class Document;
 }
diff --git a/dom/base/nsImageLoadingContent.h b/dom/base/nsImageLoadingContent.h
index 764b3ec3bf90..ec4286bed950 100644
--- a/dom/base/nsImageLoadingContent.h
+++ b/dom/base/nsImageLoadingContent.h
@@ -21,7 +21,6 @@
 #include "nsIContentPolicy.h"
 #include "nsIImageLoadingContent.h"
 #include "nsIRequest.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/Promise.h"
 #include "nsAttrValue.h"
@@ -35,6 +34,8 @@ class imgRequestProxy;
 
 namespace mozilla {
 class AsyncEventDispatcher;
+class ErrorResult;
+
 namespace dom {
 struct BindContext;
 class Document;
diff --git a/dom/base/nsJSUtils.h b/dom/base/nsJSUtils.h
index dd1bc7262365..f5c8ebb5755c 100644
--- a/dom/base/nsJSUtils.h
+++ b/dom/base/nsJSUtils.h
@@ -15,8 +15,6 @@
  */
 
 #include "mozilla/Assertions.h"
-#include "mozilla/StaticPrefs_dom.h"
-#include "mozilla/Utf8.h"  // mozilla::Utf8Unit
 
 #include "GeckoProfiler.h"
 #include "jsapi.h"
@@ -34,6 +32,8 @@ class nsIScriptGlobalObject;
 class nsXBLPrototypeBinding;
 
 namespace mozilla {
+union Utf8Unit;
+
 namespace dom {
 class AutoJSAPI;
 class Element;
diff --git a/dom/base/nsTraversal.h b/dom/base/nsTraversal.h
index d340f5cae050..801e4a291cce 100644
--- a/dom/base/nsTraversal.h
+++ b/dom/base/nsTraversal.h
@@ -13,11 +13,14 @@
 
 #include "nsCOMPtr.h"
 #include "mozilla/dom/CallbackObject.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/NodeFilterBinding.h"
 
 class nsINode;
 
+namespace mozilla {
+class ErrorResult;
+}
+
 class nsTraversal {
  public:
   nsTraversal(nsINode* aRoot, uint32_t aWhatToShow,
diff --git a/dom/base/nsWrapperCache.h b/dom/base/nsWrapperCache.h
index acb7c34100ea..88c170acb359 100644
--- a/dom/base/nsWrapperCache.h
+++ b/dom/base/nsWrapperCache.h
@@ -10,8 +10,6 @@
 #include "nsCycleCollectionParticipant.h"
 #include "mozilla/Assertions.h"
 #include "js/HeapAPI.h"
-#include "js/Id.h"     // must come before js/RootingAPI.h
-#include "js/Value.h"  // must come before js/RootingAPI.h
 #include "js/RootingAPI.h"
 #include "js/TracingAPI.h"
 #include "jsfriendapi.h"
diff --git a/dom/bindings/CallbackObject.h b/dom/bindings/CallbackObject.h
index 883da716f5ed..296402920141 100644
--- a/dom/bindings/CallbackObject.h
+++ b/dom/bindings/CallbackObject.h
@@ -17,28 +17,47 @@
 #ifndef mozilla_dom_CallbackObject_h
 #define mozilla_dom_CallbackObject_h
 
-#include "nsISupports.h"
-#include "nsISupportsImpl.h"
-#include "nsCycleCollectionParticipant.h"
+#include <cstddef>
+#include <cstdint>
+#include <utility>
+#include "js/RootingAPI.h"
 #include "js/Wrapper.h"
-#include "mozilla/Assertions.h"
-#include "mozilla/ErrorResult.h"
-#include "mozilla/HoldDropJSObjects.h"
-#include "mozilla/MemoryReporting.h"
-#include "mozilla/OwningNonNull.h"
-#include "mozilla/dom/ScriptSettings.h"
-#include "mozilla/dom/BindingCallContext.h"
-#include "nsWrapperCache.h"
-#include "nsJSEnvironment.h"
-#include "xpcpublic.h"
 #include "jsapi.h"
-#include "js/ContextOptions.h"
-#include "js/Object.h"  // JS::GetCompartment
-#include "js/TracingAPI.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/BindingCallContext.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsID.h"
+#include "nsIGlobalObject.h"
+#include "nsISupports.h"
+#include "nsISupportsUtils.h"
+#include "nsStringFwd.h"
+
+class JSAutoRealm;
+class JSObject;
+class JSTracer;
+class nsCycleCollectionTraversalCallback;
+struct JSContext;
+
+namespace JS {
+class AutoSetAsyncStackForNewCalls;
+class Realm;
+class Value;
+}  // namespace JS
 
 namespace mozilla {
 
+class ErrorResult;
 class PromiseJobRunnable;
+template <class T>
+class OwningNonNull;
 
 namespace dom {
 
diff --git a/dom/bindings/IterableIterator.h b/dom/bindings/IterableIterator.h
index 27aa2d6734fd..590c70e3ac0c 100644
--- a/dom/bindings/IterableIterator.h
+++ b/dom/bindings/IterableIterator.h
@@ -27,14 +27,12 @@
 #ifndef mozilla_dom_IterableIterator_h
 #define mozilla_dom_IterableIterator_h
 
+#include "js/TypeDecls.h"
+#include "js/Value.h"
 #include "nsISupports.h"
-#include "nsWrapperCache.h"
-#include "nsPIDOMWindow.h"
-#include "nsCOMPtr.h"
+#include "mozilla/dom/IterableIteratorBinding.h"
 #include "mozilla/dom/RootedDictionary.h"
 #include "mozilla/dom/ToJSValue.h"
-#include "js/Wrapper.h"
-#include "mozilla/dom/IterableIteratorBinding.h"
 
 namespace mozilla {
 namespace dom {
diff --git a/dom/bindings/PrimitiveConversions.h b/dom/bindings/PrimitiveConversions.h
index e25b5b374481..c6f0daee1c69 100644
--- a/dom/bindings/PrimitiveConversions.h
+++ b/dom/bindings/PrimitiveConversions.h
@@ -18,7 +18,6 @@
 #include "jsapi.h"
 #include "js/Conversions.h"
 #include "mozilla/Assertions.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/FloatingPoint.h"
 #include "mozilla/dom/BindingCallContext.h"
 
diff --git a/dom/bindings/ToJSValue.h b/dom/bindings/ToJSValue.h
index 97177d6503e6..63866f06cac0 100644
--- a/dom/bindings/ToJSValue.h
+++ b/dom/bindings/ToJSValue.h
@@ -7,24 +7,37 @@
 #ifndef mozilla_dom_ToJSValue_h
 #define mozilla_dom_ToJSValue_h
 
-#include "mozilla/Assertions.h"
-#include "mozilla/UniquePtr.h"
-#include "mozilla/dom/BindingUtils.h"
-#include "mozilla/dom/CallbackObject.h"
-#include "mozilla/dom/NonRefcountedDOMObject.h"
-#include "mozilla/dom/TypedArray.h"
-#include "jsapi.h"
-#include "js/Array.h"  // JS::NewArrayObject
-#include "nsISupports.h"
-#include "nsTArray.h"
-#include "nsWrapperCache.h"
-#include <type_traits>
+#include <cstddef>  // for size_t
+#include <cstdint>  // for int32_t, int64_t, uint32_t, uint64_t
+#include <type_traits>  // for is_base_of, enable_if_t, enable_if, is_pointer, is_same, void_t
+#include <utility>          // for forward
+#include "ErrorList.h"      // for nsresult
+#include "js/Array.h"       // for NewArrayObject
+#include "js/GCVector.h"    // for RootedVector, MutableWrappedPtrOperations
+#include "js/RootingAPI.h"  // for MutableHandle, Rooted, Handle, Heap
+#include "js/Value.h"       // for Value
+#include "js/ValueArray.h"  // for HandleValueArray
+#include "jsapi.h"          // for CurrentGlobalOrNull
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT, MOZ_ASSERT_HELPER1
+#include "mozilla/Attributes.h"        // for MOZ_MUST_USE
+#include "mozilla/UniquePtr.h"         // for UniquePtr
+#include "mozilla/Unused.h"            // for Unused
+#include "mozilla/dom/BindingUtils.h"  // for MaybeWrapValue, MaybeWrapObjectOrNullValue, XPCOMObjectToJsval, GetOrCreateDOMReflector
+#include "mozilla/dom/CallbackObject.h"  // for CallbackObject
+#include "nsID.h"                        // for NS_GET_TEMPLATE_IID, nsIID
+#include "nsISupports.h"                 // for nsISupports
+#include "nsStringFwd.h"                 // for nsAString
+#include "nsTArrayForwardDeclare.h"
+#include "xpcObjectHelper.h"  // for xpcObjectHelper
 
 namespace mozilla {
 namespace dom {
 
+class CallbackObject;
 class Promise;
 class WindowProxyHolder;
+template <typename TypedArrayType>
+class TypedArrayCreator;
 
 // If ToJSValue returns false, it must set an exception on the
 // JSContext.
diff --git a/dom/bindings/test/WrapperCachedNonISupportsTestInterface.h b/dom/bindings/test/WrapperCachedNonISupportsTestInterface.h
index 45d563190f98..0b986325b2a3 100644
--- a/dom/bindings/test/WrapperCachedNonISupportsTestInterface.h
+++ b/dom/bindings/test/WrapperCachedNonISupportsTestInterface.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
diff --git a/dom/cache/ReadStream.h b/dom/cache/ReadStream.h
index 7a2e4b5b82e9..21c838099ead 100644
--- a/dom/cache/ReadStream.h
+++ b/dom/cache/ReadStream.h
@@ -7,7 +7,6 @@
 #ifndef mozilla_dom_cache_ReadStream_h
 #define mozilla_dom_cache_ReadStream_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/SafeRefPtr.h"
 #include "mozilla/ipc/FileDescriptor.h"
 #include "mozilla/RefPtr.h"
@@ -18,6 +17,8 @@
 #include "nsTArrayForwardDeclare.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace ipc {
 class AutoIPCStream;
 }  // namespace ipc
diff --git a/dom/canvas/CanvasPath.h b/dom/canvas/CanvasPath.h
index 7c31a1180b08..7e109a96b505 100644
--- a/dom/canvas/CanvasPath.h
+++ b/dom/canvas/CanvasPath.h
@@ -10,9 +10,10 @@
 #include "nsWrapperCache.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 enum class CanvasWindingRule : uint8_t;
diff --git a/dom/canvas/CanvasRenderingContext2D.h b/dom/canvas/CanvasRenderingContext2D.h
index 07b619491da0..211de441b360 100644
--- a/dom/canvas/CanvasRenderingContext2D.h
+++ b/dom/canvas/CanvasRenderingContext2D.h
@@ -13,7 +13,6 @@
 #include "mozilla/gfx/2D.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/EnumeratedArray.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/SurfaceFromElementResult.h"
 #include "mozilla/UniquePtr.h"
@@ -28,6 +27,7 @@ class nsGlobalWindowInner;
 class nsXULElement;
 
 namespace mozilla {
+class ErrorResult;
 class PresShell;
 
 namespace gl {
diff --git a/dom/canvas/WebGLContext.h b/dom/canvas/WebGLContext.h
index 0537222476cc..9bc03fcf2e11 100644
--- a/dom/canvas/WebGLContext.h
+++ b/dom/canvas/WebGLContext.h
@@ -20,7 +20,6 @@
 #include "mozilla/dom/Nullable.h"
 #include "mozilla/dom/TypedArray.h"
 #include "mozilla/EnumeratedArray.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/Mutex.h"
 #include "mozilla/UniquePtr.h"
diff --git a/dom/clients/api/ClientDOMUtil.h b/dom/clients/api/ClientDOMUtil.h
index d71ad6f65fe3..485e6f6c07ac 100644
--- a/dom/clients/api/ClientDOMUtil.h
+++ b/dom/clients/api/ClientDOMUtil.h
@@ -10,7 +10,6 @@
 #include "mozilla/dom/ClientOpPromise.h"
 #include "mozilla/dom/DOMMozPromiseRequestHolder.h"
 #include "mozilla/dom/WorkerPrivate.h"
-#include "mozilla/ErrorResult.h"
 
 class nsIGlobalObject;
 
diff --git a/dom/clients/manager/ClientHandleParent.h b/dom/clients/manager/ClientHandleParent.h
index 5f2a7e842b03..3b0219a48082 100644
--- a/dom/clients/manager/ClientHandleParent.h
+++ b/dom/clients/manager/ClientHandleParent.h
@@ -7,7 +7,6 @@
 #define _mozilla_dom_ClientHandleParent_h
 
 #include "mozilla/dom/PClientHandleParent.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
 namespace dom {
diff --git a/dom/clients/manager/ClientInfo.h b/dom/clients/manager/ClientInfo.h
index 649b42b1c4f3..fd5f874b09f5 100644
--- a/dom/clients/manager/ClientInfo.h
+++ b/dom/clients/manager/ClientInfo.h
@@ -8,10 +8,14 @@
 #define _mozilla_dom_ClientInfo_h
 
 #include "X11UndefineNone.h"
-#include "mozilla/dom/ClientBinding.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/UniquePtr.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+
+class nsIPrincipal;
+struct nsID;
 
 namespace mozilla {
 
@@ -23,6 +27,8 @@ class PrincipalInfo;
 namespace dom {
 
 class IPCClientInfo;
+enum class FrameType : uint8_t;
+enum class ClientType : uint8_t;
 
 // This class provides a simple structure that represents a global living
 // in the system.  Its thread safe and can be transferred across process
diff --git a/dom/clients/manager/ClientOpPromise.h b/dom/clients/manager/ClientOpPromise.h
index 150c6494daf7..3658a8aabc82 100644
--- a/dom/clients/manager/ClientOpPromise.h
+++ b/dom/clients/manager/ClientOpPromise.h
@@ -6,10 +6,11 @@
 #ifndef _mozilla_dom_ClientOpPromise_h
 #define _mozilla_dom_ClientOpPromise_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/MozPromise.h"
 
 namespace mozilla {
+class CopyableErrorResult;
+
 namespace dom {
 
 class ClientOpResult;
diff --git a/dom/console/Console.h b/dom/console/Console.h
index 9c028c7f5380..05d83c365a7e 100644
--- a/dom/console/Console.h
+++ b/dom/console/Console.h
@@ -7,19 +7,18 @@
 #ifndef mozilla_dom_Console_h
 #define mozilla_dom_Console_h
 
+#include "domstubs.h"
 #include "mozilla/dom/ConsoleBinding.h"
-#include "mozilla/JSObjectHolder.h"
 #include "mozilla/TimeStamp.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsDataHashtable.h"
 #include "nsHashKeys.h"
 #include "nsIObserver.h"
 #include "nsWeakReference.h"
-#include "nsDOMNavigationTiming.h"
-#include "nsPIDOMWindow.h"
 
 class nsIConsoleAPIStorage;
-class nsIPrincipal;
+class nsIGlobalObject;
+class nsPIDOMWindowInner;
 class nsIStackFrame;
 
 namespace mozilla {
@@ -28,7 +27,6 @@ namespace dom {
 class AnyCallback;
 class ConsoleCallData;
 class ConsoleInstance;
-class ConsoleInstanceDumpCallback;
 class ConsoleRunnable;
 class ConsoleCallDataRunnable;
 class ConsoleProfileRunnable;
diff --git a/dom/events/DataTransferItem.h b/dom/events/DataTransferItem.h
index f80b358493cc..48c6784f7df7 100644
--- a/dom/events/DataTransferItem.h
+++ b/dom/events/DataTransferItem.h
@@ -7,12 +7,13 @@
 #ifndef mozilla_dom_DataTransferItem_h
 #define mozilla_dom_DataTransferItem_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/DataTransfer.h"
 #include "mozilla/dom/DOMString.h"
 #include "mozilla/dom/File.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class FileSystemEntry;
diff --git a/dom/events/Event.h b/dom/events/Event.h
index 50901194e38b..c8dd5d89110f 100644
--- a/dom/events/Event.h
+++ b/dom/events/Event.h
@@ -7,28 +7,33 @@
 #ifndef mozilla_dom_Event_h_
 #define mozilla_dom_Event_h_
 
-#include "mozilla/Attributes.h"
-#include "mozilla/BasicEvents.h"
-#include "nsISupports.h"
-#include "nsCOMPtr.h"
-#include "nsPIDOMWindow.h"
-#include "nsPoint.h"
-#include "nsCycleCollectionParticipant.h"
-#include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/dom/EventBinding.h"
-#include "mozilla/dom/PopupBlocker.h"
-#include "nsIScriptGlobalObject.h"
+#include <cstdint>
 #include "Units.h"
 #include "js/TypeDecls.h"
-#include "nsIGlobalObject.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BasicEvents.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsID.h"
+#include "nsISupports.h"
+#include "nsStringFwd.h"
+#include "nsWrapperCache.h"
 
 // XXX(Bug 1674080) Remove this and let Codegen.py generate it instead when
 // needed.
 #include "mozilla/HoldDropJSObjects.h"
 
-class nsIContent;
-class nsPresContext;
 class PickleIterator;
+class nsCycleCollectionTraversalCallback;
+class nsIContent;
+class nsIGlobalObject;
+class nsIPrincipal;
+class nsPIDOMWindowInner;
+class nsPresContext;
 
 namespace IPC {
 class Message;
@@ -39,6 +44,7 @@ namespace dom {
 
 class BeforeUnloadEvent;
 class CustomEvent;
+class Document;
 class DragEvent;
 class EventTarget;
 class EventMessageAutoOverride;
@@ -51,6 +57,8 @@ class TimeEvent;
 class UIEvent;
 class WantsPopupControlCheck;
 class XULCommandEvent;
+struct EventInit;
+
 #define GENERATED_EVENT(EventClass_) class EventClass_;
 #include "mozilla/dom/GeneratedEventList.h"
 #undef GENERATED_EVENT
diff --git a/dom/events/TextClause.h b/dom/events/TextClause.h
index ee59464d2343..7220d1976c0b 100644
--- a/dom/events/TextClause.h
+++ b/dom/events/TextClause.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsPIDOMWindow.h"
diff --git a/dom/fetch/Fetch.h b/dom/fetch/Fetch.h
index cbde04303fc6..d9176a4c20e9 100644
--- a/dom/fetch/Fetch.h
+++ b/dom/fetch/Fetch.h
@@ -13,7 +13,6 @@
 #include "nsString.h"
 
 #include "mozilla/DebugOnly.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/AbortSignal.h"
 #include "mozilla/dom/BodyConsumer.h"
 #include "mozilla/dom/BodyStream.h"
@@ -25,6 +24,8 @@ class nsIGlobalObject;
 class nsIEventTarget;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BlobOrArrayBufferViewOrArrayBufferOrFormDataOrURLSearchParamsOrUSVString;
diff --git a/dom/fetch/FetchUtil.h b/dom/fetch/FetchUtil.h
index be20d3c1948f..5907e209a4f7 100644
--- a/dom/fetch/FetchUtil.h
+++ b/dom/fetch/FetchUtil.h
@@ -10,7 +10,6 @@
 #include "nsString.h"
 #include "nsError.h"
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/FormData.h"
 
diff --git a/dom/file/BaseBlobImpl.h b/dom/file/BaseBlobImpl.h
index 610849b0a167..6332278ade0a 100644
--- a/dom/file/BaseBlobImpl.h
+++ b/dom/file/BaseBlobImpl.h
@@ -8,6 +8,7 @@
 #define mozilla_dom_BaseBlobImpl_h
 
 #include "mozilla/dom/BlobImpl.h"
+#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
 namespace dom {
diff --git a/dom/file/Blob.h b/dom/file/Blob.h
index 8c06e67b8450..120428d4fe31 100644
--- a/dom/file/Blob.h
+++ b/dom/file/Blob.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_Blob_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/BlobImpl.h"
 #include "mozilla/dom/BodyConsumer.h"
@@ -21,6 +20,8 @@ class nsIGlobalObject;
 class nsIInputStream;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct BlobPropertyBag;
diff --git a/dom/file/BlobImpl.h b/dom/file/BlobImpl.h
index a3bfcde4fdfd..1177568ca8b1 100644
--- a/dom/file/BlobImpl.h
+++ b/dom/file/BlobImpl.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_BlobImpl_h
 
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "nsISupportsImpl.h"
 #include "nsString.h"
 
@@ -22,6 +21,8 @@
 class nsIInputStream;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 // This is the abstract class for any File backend. It must be nsISupports
diff --git a/dom/file/FileCreatorHelper.h b/dom/file/FileCreatorHelper.h
index 78eb7d7a6953..f0b666cc58af 100644
--- a/dom/file/FileCreatorHelper.h
+++ b/dom/file/FileCreatorHelper.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_FileCreatorHelper_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 #include "nsISupportsImpl.h"
 
@@ -22,6 +21,8 @@ class nsIFile;
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct ChromeFilePropertyBag;
diff --git a/dom/file/MultipartBlobImpl.h b/dom/file/MultipartBlobImpl.h
index 46f0855bf130..6670ed5d446c 100644
--- a/dom/file/MultipartBlobImpl.h
+++ b/dom/file/MultipartBlobImpl.h
@@ -11,11 +11,12 @@
 
 #include "Blob.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/dom/BaseBlobImpl.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 // This is just a sentinel value to be sure that we don't call
diff --git a/dom/filesystem/Directory.h b/dom/filesystem/Directory.h
index 61a5667f127b..11f1132cdaf2 100644
--- a/dom/filesystem/Directory.h
+++ b/dom/filesystem/Directory.h
@@ -8,13 +8,14 @@
 #define mozilla_dom_Directory_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/File.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class FileSystemBase;
diff --git a/dom/filesystem/FileSystemTaskBase.h b/dom/filesystem/FileSystemTaskBase.h
index 4ed4ac9d9670..3d440403cc49 100644
--- a/dom/filesystem/FileSystemTaskBase.h
+++ b/dom/filesystem/FileSystemTaskBase.h
@@ -7,13 +7,14 @@
 #ifndef mozilla_dom_FileSystemTaskBase_h
 #define mozilla_dom_FileSystemTaskBase_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/FileSystemRequestParent.h"
 #include "mozilla/dom/PFileSystemRequestChild.h"
 #include "nsIGlobalObject.h"
 #include "nsThreadUtils.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BlobImpl;
diff --git a/dom/filesystem/GetDirectoryListingTask.h b/dom/filesystem/GetDirectoryListingTask.h
index 23e05848048a..afb5296ac54e 100644
--- a/dom/filesystem/GetDirectoryListingTask.h
+++ b/dom/filesystem/GetDirectoryListingTask.h
@@ -9,9 +9,10 @@
 
 #include "mozilla/dom/Directory.h"
 #include "mozilla/dom/FileSystemTaskBase.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BlobImpl;
diff --git a/dom/filesystem/GetFileOrDirectoryTask.h b/dom/filesystem/GetFileOrDirectoryTask.h
index 7a814faf8144..8d15d9804f40 100644
--- a/dom/filesystem/GetFileOrDirectoryTask.h
+++ b/dom/filesystem/GetFileOrDirectoryTask.h
@@ -9,9 +9,10 @@
 
 #include "mozilla/dom/Directory.h"
 #include "mozilla/dom/FileSystemTaskBase.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BlobImpl;
diff --git a/dom/filesystem/GetFilesTask.h b/dom/filesystem/GetFilesTask.h
index 0c6a64d88e55..6f6f15e8796a 100644
--- a/dom/filesystem/GetFilesTask.h
+++ b/dom/filesystem/GetFilesTask.h
@@ -10,9 +10,10 @@
 #include "mozilla/dom/Directory.h"
 #include "mozilla/dom/FileSystemTaskBase.h"
 #include "mozilla/dom/GetFilesHelper.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BlobImpl;
diff --git a/dom/filesystem/compat/FileSystem.h b/dom/filesystem/compat/FileSystem.h
index 0654b442137c..298d6ead90e2 100644
--- a/dom/filesystem/compat/FileSystem.h
+++ b/dom/filesystem/compat/FileSystem.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_FileSystem_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
diff --git a/dom/filesystem/compat/FileSystemDirectoryReader.h b/dom/filesystem/compat/FileSystemDirectoryReader.h
index 4c3ac8132867..5aa9dce79fdf 100644
--- a/dom/filesystem/compat/FileSystemDirectoryReader.h
+++ b/dom/filesystem/compat/FileSystemDirectoryReader.h
@@ -8,13 +8,14 @@
 #define mozilla_dom_FileSystemDirectoryReader_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/FileSystemDirectoryEntry.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Directory;
diff --git a/dom/filesystem/compat/FileSystemEntry.h b/dom/filesystem/compat/FileSystemEntry.h
index 307dd3bbf457..ffdafc0a2cce 100644
--- a/dom/filesystem/compat/FileSystemEntry.h
+++ b/dom/filesystem/compat/FileSystemEntry.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_FileSystemEntry_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/FileSystemBinding.h"
 #include "nsCycleCollectionParticipant.h"
@@ -16,6 +15,8 @@
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class FileSystem;
diff --git a/dom/gamepad/Gamepad.h b/dom/gamepad/Gamepad.h
index d063482dee7c..a6e0a5cdd0cb 100644
--- a/dom/gamepad/Gamepad.h
+++ b/dom/gamepad/Gamepad.h
@@ -7,7 +7,6 @@
 #ifndef mozilla_dom_gamepad_Gamepad_h
 #define mozilla_dom_gamepad_Gamepad_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/GamepadBinding.h"
 #include "mozilla/dom/GamepadButton.h"
 #include "mozilla/dom/GamepadPose.h"
diff --git a/dom/html/HTMLOptionsCollection.h b/dom/html/HTMLOptionsCollection.h
index 2c79846a3348..97fd7ccd0732 100644
--- a/dom/html/HTMLOptionsCollection.h
+++ b/dom/html/HTMLOptionsCollection.h
@@ -11,13 +11,14 @@
 #include "nsWrapperCache.h"
 
 #include "mozilla/dom/HTMLOptionElement.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCOMPtr.h"
 #include "nsError.h"
 #include "nsGenericHTMLElement.h"
 #include "nsTArray.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class DocGroup;
diff --git a/dom/html/HTMLSelectElement.h b/dom/html/HTMLSelectElement.h
index e8f847fcc807..f4bb48497762 100644
--- a/dom/html/HTMLSelectElement.h
+++ b/dom/html/HTMLSelectElement.h
@@ -13,7 +13,6 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/UnionTypes.h"
 #include "mozilla/dom/HTMLOptionsCollection.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCheapSets.h"
 #include "nsCOMPtr.h"
 #include "nsError.h"
@@ -27,6 +26,7 @@ class nsISelectControlFrame;
 
 namespace mozilla {
 
+class ErrorResult;
 class EventChainPostVisitor;
 class EventChainPreVisitor;
 class SelectContentData;
diff --git a/dom/html/TimeRanges.h b/dom/html/TimeRanges.h
index 708d3cccda4d..302d3070e7ad 100644
--- a/dom/html/TimeRanges.h
+++ b/dom/html/TimeRanges.h
@@ -11,10 +11,10 @@
 #include "nsISupports.h"
 #include "nsTArray.h"
 #include "nsWrapperCache.h"
-#include "mozilla/ErrorResult.h"
 #include "TimeUnits.h"
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 class TimeRanges;
diff --git a/dom/html/nsGenericHTMLElement.h b/dom/html/nsGenericHTMLElement.h
index 9a3be6621f4b..0bc095abc664 100644
--- a/dom/html/nsGenericHTMLElement.h
+++ b/dom/html/nsGenericHTMLElement.h
@@ -13,7 +13,6 @@
 #include "nsIFormControl.h"
 #include "nsGkAtoms.h"
 #include "nsContentCreatorFunctions.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/DOMRect.h"
@@ -27,6 +26,7 @@ class nsIURI;
 struct nsSize;
 
 namespace mozilla {
+class ErrorResult;
 class EventChainPostVisitor;
 class EventChainPreVisitor;
 class EventChainVisitor;
diff --git a/dom/html/nsGenericHTMLFrameElement.h b/dom/html/nsGenericHTMLFrameElement.h
index 0ac600b6298e..09d607bb2c6a 100644
--- a/dom/html/nsGenericHTMLFrameElement.h
+++ b/dom/html/nsGenericHTMLFrameElement.h
@@ -8,7 +8,6 @@
 #define nsGenericHTMLFrameElement_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/nsBrowserElement.h"
 
 #include "nsFrameLoader.h"
@@ -17,6 +16,8 @@
 #include "nsIMozBrowserFrame.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 class BrowserParent;
 template <typename>
diff --git a/dom/indexedDB/Key.h b/dom/indexedDB/Key.h
index b4cb55854a62..db274be56b32 100644
--- a/dom/indexedDB/Key.h
+++ b/dom/indexedDB/Key.h
@@ -12,7 +12,6 @@
 #include "js/Array.h"  // JS::GetArrayLength
 #include "js/RootingAPI.h"
 #include "jsapi.h"
-#include "mozilla/ErrorResult.h"
 #include "nsString.h"
 
 class mozIStorageStatement;
diff --git a/dom/ipc/BrowserParent.h b/dom/ipc/BrowserParent.h
index 3929729a59d6..f4161f3dbe09 100644
--- a/dom/ipc/BrowserParent.h
+++ b/dom/ipc/BrowserParent.h
@@ -16,14 +16,9 @@
 #include "mozilla/EventForwards.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/dom/BrowserBridgeParent.h"
-#include "mozilla/dom/File.h"
 #include "mozilla/dom/PBrowserParent.h"
-#include "mozilla/dom/PContent.h"
-#include "mozilla/dom/PFilePickerParent.h"
 #include "mozilla/dom/TabContext.h"
 #include "mozilla/dom/ipc/IdType.h"
-#include "mozilla/gfx/CrossProcessPaint.h"
-#include "mozilla/layers/CompositorBridgeParent.h"
 #include "mozilla/layout/RemoteLayerTreeOwner.h"
 #include "nsCOMPtr.h"
 #include "nsIAuthPromptProvider.h"
@@ -32,17 +27,24 @@
 #include "nsIKeyEventInPluginCallback.h"
 #include "nsIRemoteTab.h"
 #include "nsIWidget.h"
-#include "nsIXULBrowserWindow.h"
 #include "nsWeakReference.h"
 
+class imgIContainer;
+class nsCycleCollectionTraversalCallback;
+class nsDocShellLoadState;
 class nsFrameLoader;
+class nsIBrowser;
 class nsIContent;
-class nsIPrincipal;
-class nsIURI;
-class nsILoadContext;
+class nsIContentSecurityPolicy;
 class nsIDocShell;
+class nsILoadContext;
+class nsIPrincipal;
+class nsIRequest;
+class nsIURI;
 class nsIWebBrowserPersistDocumentReceiver;
 class nsIWebProgress;
+class nsIXULBrowserWindow;
+class nsPIDOMWindowOuter;
 
 namespace mozilla {
 
@@ -50,17 +52,12 @@ namespace a11y {
 class DocAccessibleParent;
 }
 
-namespace layers {
-struct TextureFactoryIdentifier;
-}  // namespace layers
-
 namespace widget {
 struct IMENotification;
 }  // namespace widget
 
 namespace gfx {
 class SourceSurface;
-class DataSourceSurface;
 }  // namespace gfx
 
 namespace dom {
diff --git a/dom/ipc/ClonedErrorHolder.h b/dom/ipc/ClonedErrorHolder.h
index f406f2abdf36..1eb6af4b274b 100644
--- a/dom/ipc/ClonedErrorHolder.h
+++ b/dom/ipc/ClonedErrorHolder.h
@@ -13,12 +13,13 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/StructuredCloneHolder.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 
 class nsIGlobalObject;
 class nsQueryActorChild;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class ClonedErrorHolder final {
diff --git a/dom/ipc/ContentChild.h b/dom/ipc/ContentChild.h
index 284c93ea36c9..6981aa0f96c3 100644
--- a/dom/ipc/ContentChild.h
+++ b/dom/ipc/ContentChild.h
@@ -8,14 +8,13 @@
 #define mozilla_dom_ContentChild_h
 
 #include "mozilla/Atomics.h"
-#include "mozilla/dom/MediaControlKeySource.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/GetFilesHelper.h"
 #include "mozilla/dom/PContentChild.h"
 #include "mozilla/dom/ProcessActor.h"
 #include "mozilla/dom/RemoteType.h"
 #include "mozilla/ipc/InputStreamUtils.h"
 #include "mozilla/ipc/ProtocolUtils.h"
-#include "mozilla/widget/ThemeChangeKind.h"
-#include "mozilla/LookAndFeel.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/UniquePtr.h"
 #include "nsClassHashtable.h"
@@ -46,10 +45,19 @@ class RemoteSpellcheckEngineChild;
 class ChildProfilerController;
 class BenchmarkStorageChild;
 
+namespace ipc {
+class PChildToParentStreamChild;
+class PFileDescriptorSetChild;
+}  // namespace ipc
+
 namespace loader {
 class PScriptCacheChild;
 }
 
+namespace widget {
+enum class ThemeChangeKind : uint8_t;
+}
+
 using mozilla::loader::PScriptCacheChild;
 
 #if !defined(XP_WIN)
@@ -71,8 +79,8 @@ class AlertObserver;
 class ConsoleListener;
 class ClonedMessageData;
 class BrowserChild;
-class GetFilesHelperChild;
 class TabContext;
+enum class CallerType : uint32_t;
 
 class ContentChild final : public PContentChild,
                            public nsIDOMProcessChild,
diff --git a/dom/ipc/ProcessActor.h b/dom/ipc/ProcessActor.h
index af906a3e5756..a80300b67243 100644
--- a/dom/ipc/ProcessActor.h
+++ b/dom/ipc/ProcessActor.h
@@ -7,19 +7,17 @@
 #ifndef mozilla_dom_ProcessActor_h
 #define mozilla_dom_ProcessActor_h
 
-#include "nsWrapperCache.h"
-#include "nsISupports.h"
-#include "mozilla/dom/BrowsingContext.h"
-#include "mozilla/ErrorResult.h"
-#include "nsIURI.h"
-#include "nsRefPtrHashtable.h"
-#include "nsString.h"
-#include "mozilla/dom/JSActor.h"
 #include "mozilla/dom/JSActorManager.h"
+#include "nsStringFwd.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
+class JSActorProtocol;
+class JSActorService;
+
 // Common base class for Content{Parent, Child} and InProcess{Parent, Child}.
 class ProcessActor : public JSActorManager {
  protected:
diff --git a/dom/ipc/RemoteBrowser.h b/dom/ipc/RemoteBrowser.h
index 40fdc21aae7f..41a890c73768 100644
--- a/dom/ipc/RemoteBrowser.h
+++ b/dom/ipc/RemoteBrowser.h
@@ -7,19 +7,15 @@
 #ifndef mozilla_dom_ipc_RemoteBrowser_h
 #define mozilla_dom_ipc_RemoteBrowser_h
 
-#include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/ipc/IdType.h"
-#include "mozilla/dom/EffectsInfo.h"
 #include "mozilla/layers/LayersTypes.h"
-#include "nsILoadContext.h"
-#include "nsIPrincipal.h"
 #include "nsISupports.h"
-#include "nsISupportsImpl.h"
-#include "nsIURI.h"
 #include "nsRect.h"
 #include "Units.h"
 
+class nsDocShellLoadState;
 class nsFrameLoader;
+class nsILoadContext;
 class nsIContent;
 
 namespace mozilla {
@@ -28,6 +24,8 @@ namespace dom {
 
 class BrowserHost;
 class BrowserBridgeHost;
+class BrowsingContext;
+class EffectsInfo;
 class OwnerShowInfo;
 
 /**
diff --git a/dom/ipc/WindowGlobalActor.h b/dom/ipc/WindowGlobalActor.h
index 0957e67ffea0..7ab19c292ecc 100644
--- a/dom/ipc/WindowGlobalActor.h
+++ b/dom/ipc/WindowGlobalActor.h
@@ -10,7 +10,6 @@
 #include "nsWrapperCache.h"
 #include "nsISupports.h"
 #include "mozilla/dom/BrowsingContext.h"
-#include "mozilla/ErrorResult.h"
 #include "nsIURI.h"
 #include "nsString.h"
 #include "mozilla/dom/JSActor.h"
@@ -18,6 +17,8 @@
 #include "mozilla/dom/WindowGlobalTypes.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 // Common base class for WindowGlobal{Parent, Child}.
diff --git a/dom/ipc/jsactor/JSActor.h b/dom/ipc/jsactor/JSActor.h
index 7c3d9584b6c4..5bdfac30b30e 100644
--- a/dom/ipc/jsactor/JSActor.h
+++ b/dom/ipc/jsactor/JSActor.h
@@ -10,7 +10,6 @@
 #include "js/TypeDecls.h"
 #include "ipc/IPCMessageUtils.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/PromiseNativeHandler.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsDataHashtable.h"
@@ -20,6 +19,8 @@ class nsIGlobalObject;
 class nsQueryJSActor;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 namespace ipc {
diff --git a/dom/ipc/jsactor/JSActorManager.h b/dom/ipc/jsactor/JSActorManager.h
index 923f7bdced38..80f4893b06d2 100644
--- a/dom/ipc/jsactor/JSActorManager.h
+++ b/dom/ipc/jsactor/JSActorManager.h
@@ -9,11 +9,12 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/dom/JSActor.h"
-#include "mozilla/ErrorResult.h"
 #include "nsRefPtrHashtable.h"
 #include "nsString.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace ipc {
 class IProtocol;
 }
diff --git a/dom/ipc/jsactor/JSActorService.h b/dom/ipc/jsactor/JSActorService.h
index cd622ccd267d..610d0fc99604 100644
--- a/dom/ipc/jsactor/JSActorService.h
+++ b/dom/ipc/jsactor/JSActorService.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_JSActorService_h
 
 #include "mozilla/dom/BrowsingContext.h"
-#include "mozilla/ErrorResult.h"
 #include "nsIURI.h"
 #include "nsRefPtrHashtable.h"
 #include "nsString.h"
@@ -19,6 +18,8 @@
 #include "mozilla/EventListenerManager.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct ProcessActorOptions;
diff --git a/dom/ipc/jsactor/JSProcessActorParent.h b/dom/ipc/jsactor/JSProcessActorParent.h
index abcc0e3feec2..239efbeb594d 100644
--- a/dom/ipc/jsactor/JSProcessActorParent.h
+++ b/dom/ipc/jsactor/JSProcessActorParent.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/JSActor.h"
@@ -18,6 +17,8 @@
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class JSProcessActorParent final : public JSActor {
diff --git a/dom/ipc/jsactor/JSProcessActorProtocol.h b/dom/ipc/jsactor/JSProcessActorProtocol.h
index 47d5ec5066ab..2230283dcf61 100644
--- a/dom/ipc/jsactor/JSProcessActorProtocol.h
+++ b/dom/ipc/jsactor/JSProcessActorProtocol.h
@@ -9,13 +9,14 @@
 
 #include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/JSActorService.h"
-#include "mozilla/ErrorResult.h"
 #include "nsIURI.h"
 #include "nsString.h"
 #include "nsTArray.h"
 #include "nsIObserver.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct ProcessActorOptions;
diff --git a/dom/ipc/jsactor/JSWindowActorChild.h b/dom/ipc/jsactor/JSWindowActorChild.h
index 77b796889a15..73521c376a90 100644
--- a/dom/ipc/jsactor/JSWindowActorChild.h
+++ b/dom/ipc/jsactor/JSWindowActorChild.h
@@ -7,24 +7,30 @@
 #ifndef mozilla_dom_JSWindowActorChild_h
 #define mozilla_dom_JSWindowActorChild_h
 
-#include "js/TypeDecls.h"
-#include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
+#include "js/RootingAPI.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/RefPtr.h"
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/JSActor.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
-#include "nsWrapperCache.h"
-#include "nsIDOMProcessChild.h"
+#include "nsIGlobalObject.h"
+#include "nsISupports.h"
+#include "nsStringFwd.h"
+
+class nsIDocShell;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 template <typename>
 struct Nullable;
 
+class BrowsingContext;
 class Document;
-class WindowGlobalChild;
 class WindowProxyHolder;
 
 }  // namespace dom
diff --git a/dom/ipc/jsactor/JSWindowActorParent.h b/dom/ipc/jsactor/JSWindowActorParent.h
index 56bae19d8444..56d6fd3f7de8 100644
--- a/dom/ipc/jsactor/JSWindowActorParent.h
+++ b/dom/ipc/jsactor/JSWindowActorParent.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/JSActor.h"
@@ -17,6 +16,8 @@
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class WindowGlobalParent;
diff --git a/dom/ipc/jsactor/JSWindowActorProtocol.h b/dom/ipc/jsactor/JSWindowActorProtocol.h
index 03be5f4888b0..993e6b4e6ed3 100644
--- a/dom/ipc/jsactor/JSWindowActorProtocol.h
+++ b/dom/ipc/jsactor/JSWindowActorProtocol.h
@@ -10,7 +10,6 @@
 #include "mozilla/dom/BrowsingContext.h"
 #include "mozilla/dom/JSActorService.h"
 #include "mozilla/extensions/MatchPattern.h"
-#include "mozilla/ErrorResult.h"
 #include "nsIURI.h"
 #include "nsString.h"
 #include "nsTArray.h"
@@ -18,6 +17,8 @@
 #include "nsIDOMEventListener.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct WindowActorOptions;
diff --git a/dom/media/MediaStreamError.h b/dom/media/MediaStreamError.h
index 8beb56679b1a..68c35b53e59d 100644
--- a/dom/media/MediaStreamError.h
+++ b/dom/media/MediaStreamError.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_MediaStreamError_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 #include "js/TypeDecls.h"
 #include "nsPIDOMWindow.h"
diff --git a/dom/media/eme/CDMProxy.h b/dom/media/eme/CDMProxy.h
index 9ab15958c45b..aec178bc4ef5 100644
--- a/dom/media/eme/CDMProxy.h
+++ b/dom/media/eme/CDMProxy.h
@@ -9,7 +9,6 @@
 
 #include "mozilla/CDMCaps.h"
 #include "mozilla/DataMutex.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/MozPromise.h"
 
 #include "mozilla/dom/MediaKeyMessageEvent.h"
@@ -18,6 +17,7 @@
 #include "nsIThread.h"
 
 namespace mozilla {
+class ErrorResult;
 class MediaRawData;
 class ChromiumCDMProxy;
 
diff --git a/dom/media/eme/DecryptorProxyCallback.h b/dom/media/eme/DecryptorProxyCallback.h
index 05d2b4b4f021..6395bf8f6bd2 100644
--- a/dom/media/eme/DecryptorProxyCallback.h
+++ b/dom/media/eme/DecryptorProxyCallback.h
@@ -9,7 +9,10 @@
 #include "mozilla/dom/MediaKeyStatusMapBinding.h"     // For MediaKeyStatus
 #include "mozilla/dom/MediaKeyMessageEventBinding.h"  // For MediaKeyMessageType
 #include "mozilla/CDMProxy.h"
-#include "mozilla/ErrorResult.h"
+
+namespace mozilla {
+class ErrorResult;
+}
 
 class DecryptorProxyCallback {
  public:
diff --git a/dom/media/eme/MediaKeyError.h b/dom/media/eme/MediaKeyError.h
index 61fdee38e986..9e6007df39cf 100644
--- a/dom/media/eme/MediaKeyError.h
+++ b/dom/media/eme/MediaKeyError.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_MediaKeyError_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 #include "mozilla/dom/Event.h"
 #include "js/TypeDecls.h"
diff --git a/dom/media/eme/MediaKeyMessageEvent.h b/dom/media/eme/MediaKeyMessageEvent.h
index 420c1731d90c..400439b065fb 100644
--- a/dom/media/eme/MediaKeyMessageEvent.h
+++ b/dom/media/eme/MediaKeyMessageEvent.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_MediaKeyMessageEvent_h__
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "nsCOMPtr.h"
@@ -18,6 +17,8 @@
 #include "mozilla/dom/MediaKeyMessageEventBinding.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct MediaKeyMessageEventInit;
diff --git a/dom/media/eme/MediaKeySession.h b/dom/media/eme/MediaKeySession.h
index 3912bfef164f..e19488c311b1 100644
--- a/dom/media/eme/MediaKeySession.h
+++ b/dom/media/eme/MediaKeySession.h
@@ -9,7 +9,6 @@
 
 #include "DecoderDoctorLogger.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "mozilla/DOMEventTargetHelper.h"
 #include "nsCOMPtr.h"
@@ -24,6 +23,7 @@
 struct JSContext;
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 class MediaKeySession;
diff --git a/dom/media/eme/MediaKeyStatusMap.h b/dom/media/eme/MediaKeyStatusMap.h
index 3eba0a9c6587..653e95093acf 100644
--- a/dom/media/eme/MediaKeyStatusMap.h
+++ b/dom/media/eme/MediaKeyStatusMap.h
@@ -7,7 +7,6 @@
 #ifndef mozilla_dom_MediaKeyStatuses_h
 #define mozilla_dom_MediaKeyStatuses_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Attributes.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
@@ -19,6 +18,8 @@
 class nsPIDOMWindowInner;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class ArrayBufferViewOrArrayBuffer;
diff --git a/dom/media/eme/MediaKeySystemAccess.h b/dom/media/eme/MediaKeySystemAccess.h
index 1ec4a46cd867..50b36b081ef8 100644
--- a/dom/media/eme/MediaKeySystemAccess.h
+++ b/dom/media/eme/MediaKeySystemAccess.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_MediaKeySystemAccess_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 
@@ -21,6 +20,7 @@
 namespace mozilla {
 
 class DecoderDoctorDiagnostics;
+class ErrorResult;
 
 namespace dom {
 
diff --git a/dom/media/eme/mediadrm/MediaDrmCDMCallbackProxy.h b/dom/media/eme/mediadrm/MediaDrmCDMCallbackProxy.h
index 9d3a752335f3..be2bb39dbfdc 100644
--- a/dom/media/eme/mediadrm/MediaDrmCDMCallbackProxy.h
+++ b/dom/media/eme/mediadrm/MediaDrmCDMCallbackProxy.h
@@ -8,11 +8,12 @@
 #define MediaDrmCDMCallbackProxy_h_
 
 #include "mozilla/CDMProxy.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/DecryptorProxyCallback.h"
 
 namespace mozilla {
 class CDMProxy;
+class ErrorResult;
+
 // Proxies call backs from the MediaDrmProxy -> MediaDrmProxySupport back to the
 // MediaKeys object on the main thread. We used annotation calledFrom = "gecko"
 // to ensure running on main thread.
diff --git a/dom/media/gmp/ChromiumCDMCallback.h b/dom/media/gmp/ChromiumCDMCallback.h
index 3481a81ec6fa..affcad3eb702 100644
--- a/dom/media/gmp/ChromiumCDMCallback.h
+++ b/dom/media/gmp/ChromiumCDMCallback.h
@@ -7,11 +7,14 @@
 #define ChromiumCDMCallback_h_
 
 #include "mozilla/CDMProxy.h"
-#include "mozilla/ErrorResult.h"                      // For ErrorResult
 #include "mozilla/dom/MediaKeyStatusMapBinding.h"     // For MediaKeyStatus
 #include "mozilla/dom/MediaKeyMessageEventBinding.h"  // For MediaKeyMessageType
 #include "mozilla/gmp/GMPTypes.h"                     // For CDMKeyInformation
 
+namespace mozilla {
+class ErrorResult;
+}
+
 class ChromiumCDMCallback {
  public:
   virtual ~ChromiumCDMCallback() = default;
diff --git a/dom/media/gmp/ChromiumCDMParent.h b/dom/media/gmp/ChromiumCDMParent.h
index 00527841d8ba..37b1734d33a1 100644
--- a/dom/media/gmp/ChromiumCDMParent.h
+++ b/dom/media/gmp/ChromiumCDMParent.h
@@ -15,7 +15,6 @@
 #include "nsDataHashtable.h"
 #include "PlatformDecoderModule.h"
 #include "ImageContainer.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Span.h"
 #include "ReorderQueue.h"
 
@@ -23,6 +22,7 @@ class ChromiumCDMCallback;
 
 namespace mozilla {
 
+class ErrorResult;
 class MediaRawData;
 class ChromiumCDMProxy;
 
diff --git a/dom/media/gmp/ChromiumCDMProxy.h b/dom/media/gmp/ChromiumCDMProxy.h
index 5c353c29bfc3..b543408aa197 100644
--- a/dom/media/gmp/ChromiumCDMProxy.h
+++ b/dom/media/gmp/ChromiumCDMProxy.h
@@ -8,12 +8,12 @@
 #define ChromiumCDMProxy_h_
 
 #include "mozilla/AbstractThread.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/CDMProxy.h"
 #include "ChromiumCDMParent.h"
 
 namespace mozilla {
 
+class ErrorResult;
 class MediaRawData;
 class DecryptJob;
 class ChromiumCDMCallbackProxy;
diff --git a/dom/media/gmp/GMPCrashHelper.h b/dom/media/gmp/GMPCrashHelper.h
index e798fc23d12e..d1945321c063 100644
--- a/dom/media/gmp/GMPCrashHelper.h
+++ b/dom/media/gmp/GMPCrashHelper.h
@@ -9,7 +9,8 @@
 
 #  include "MainThreadUtils.h"
 #  include "nsISupportsImpl.h"
-#  include "nsPIDOMWindow.h"
+
+class nsPIDOMWindowInner;
 
 namespace mozilla {
 
diff --git a/dom/media/mediasession/MediaMetadata.h b/dom/media/mediasession/MediaMetadata.h
index a9d83d71d788..63fae8f77641 100644
--- a/dom/media/mediasession/MediaMetadata.h
+++ b/dom/media/mediasession/MediaMetadata.h
@@ -11,13 +11,14 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/MediaSessionBinding.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class MediaMetadataBase {
diff --git a/dom/media/mediasession/MediaSession.h b/dom/media/mediasession/MediaSession.h
index 83b0177e2bc9..45cfd0411492 100644
--- a/dom/media/mediasession/MediaSession.h
+++ b/dom/media/mediasession/MediaSession.h
@@ -12,7 +12,6 @@
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/MediaMetadata.h"
 #include "mozilla/dom/MediaSessionBinding.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/EnumeratedArray.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsIDocumentActivity.h"
@@ -21,6 +20,8 @@
 class nsPIDOMWindowInner;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 // https://w3c.github.io/mediasession/#position-state
diff --git a/dom/media/webaudio/AudioParamTimeline.h b/dom/media/webaudio/AudioParamTimeline.h
index 4a3fe0f8b09e..4c0c439da01d 100644
--- a/dom/media/webaudio/AudioParamTimeline.h
+++ b/dom/media/webaudio/AudioParamTimeline.h
@@ -9,7 +9,6 @@
 
 #include "AudioEventTimeline.h"
 #include "AudioNodeTrack.h"
-#include "mozilla/ErrorResult.h"
 #include "AudioSegment.h"
 
 namespace mozilla {
diff --git a/dom/media/webspeech/recognition/SpeechGrammar.h b/dom/media/webspeech/recognition/SpeechGrammar.h
index 6cd47eeabf53..ea4a6bab8ec7 100644
--- a/dom/media/webspeech/recognition/SpeechGrammar.h
+++ b/dom/media/webspeech/recognition/SpeechGrammar.h
@@ -14,9 +14,10 @@
 #include "js/TypeDecls.h"
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class GlobalObject;
diff --git a/dom/media/webvtt/TextTrackCueList.h b/dom/media/webvtt/TextTrackCueList.h
index 75623ecb1cbd..5669fe12ce49 100644
--- a/dom/media/webvtt/TextTrackCueList.h
+++ b/dom/media/webvtt/TextTrackCueList.h
@@ -11,9 +11,10 @@
 #include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class TextTrackCue;
diff --git a/dom/messagechannel/MessageChannel.h b/dom/messagechannel/MessageChannel.h
index 8837bbc3edfb..861cd3122991 100644
--- a/dom/messagechannel/MessageChannel.h
+++ b/dom/messagechannel/MessageChannel.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_MessageChannel_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
@@ -17,6 +16,8 @@
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class MessagePort;
diff --git a/dom/midi/MIDIAccess.h b/dom/midi/MIDIAccess.h
index e9d60f89de7c..99071aa526b5 100644
--- a/dom/midi/MIDIAccess.h
+++ b/dom/midi/MIDIAccess.h
@@ -9,7 +9,6 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/DOMEventTargetHelper.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Observer.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
@@ -17,6 +16,8 @@
 struct JSContext;
 
 namespace mozilla {
+class ErrorResult;
+
 // Predeclare void_t here, as including IPCMessageUtils brings in windows.h and
 // causes binding compilation problems.
 struct void_t;
diff --git a/dom/midi/MIDIOutput.h b/dom/midi/MIDIOutput.h
index 254619be5b5a..72d0efb55e7a 100644
--- a/dom/midi/MIDIOutput.h
+++ b/dom/midi/MIDIOutput.h
@@ -9,12 +9,13 @@
 
 #include "mozilla/dom/MIDIPort.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 
 struct JSContext;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class MIDIPortInfo;
diff --git a/dom/midi/MIDIPlatformService.h b/dom/midi/MIDIPlatformService.h
index d83b238b54a9..74ca04b3b8bf 100644
--- a/dom/midi/MIDIPlatformService.h
+++ b/dom/midi/MIDIPlatformService.h
@@ -10,8 +10,6 @@
 #include "nsClassHashtable.h"
 #include "mozilla/Mutex.h"
 #include "mozilla/dom/MIDIPortBinding.h"
-#include "mozilla/dom/MIDITypes.h"
-#include "mozilla/dom/MIDIPortInterface.h"
 #include "nsHashKeys.h"
 
 // XXX Avoid including this here by moving function implementations to the cpp
@@ -23,7 +21,9 @@ namespace dom {
 
 class MIDIManagerParent;
 class MIDIPortParent;
+class MIDIMessage;
 class MIDIMessageQueue;
+class MIDIPortInfo;
 
 /**
  * Base class for platform specific MIDI implementations. Handles aggregation of
diff --git a/dom/midi/MIDIPort.h b/dom/midi/MIDIPort.h
index 9e4e71ceddb7..1d12030a7135 100644
--- a/dom/midi/MIDIPort.h
+++ b/dom/midi/MIDIPort.h
@@ -11,7 +11,6 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/Observer.h"
 #include "mozilla/DOMEventTargetHelper.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/MIDIAccess.h"
 #include "mozilla/dom/MIDIPortInterface.h"
 
diff --git a/dom/network/UDPSocket.h b/dom/network/UDPSocket.h
index b32ba2c25f25..5453fe54481a 100644
--- a/dom/network/UDPSocket.h
+++ b/dom/network/UDPSocket.h
@@ -9,7 +9,6 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/DOMEventTargetHelper.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/Promise.h"
 #include "mozilla/dom/SocketCommonBinding.h"
 #include "nsIUDPSocket.h"
@@ -23,6 +22,7 @@ struct JSContext;
 //
 
 namespace mozilla {
+class ErrorResult;
 class LazyLogModule;
 
 namespace net {
diff --git a/dom/payments/MerchantValidationEvent.h b/dom/payments/MerchantValidationEvent.h
index abbf21ef5d59..b7de875ea173 100644
--- a/dom/payments/MerchantValidationEvent.h
+++ b/dom/payments/MerchantValidationEvent.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_MerchantValidationEvent_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Result.h"
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/MerchantValidationEventBinding.h"
@@ -17,6 +16,8 @@
 class nsIURI;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Promise;
diff --git a/dom/payments/PaymentMethodChangeEvent.h b/dom/payments/PaymentMethodChangeEvent.h
index 44f5e0112a10..9617214df4fd 100644
--- a/dom/payments/PaymentMethodChangeEvent.h
+++ b/dom/payments/PaymentMethodChangeEvent.h
@@ -7,7 +7,6 @@
 #ifndef mozilla_dom_PaymentMethodChangeEvent_h
 #define mozilla_dom_PaymentMethodChangeEvent_h
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/PaymentMethodChangeEventBinding.h"
 #include "mozilla/dom/PaymentRequestUpdateEvent.h"
 #include "mozilla/dom/PaymentRequest.h"
diff --git a/dom/payments/PaymentRequestUpdateEvent.h b/dom/payments/PaymentRequestUpdateEvent.h
index 8fcf2af05302..cd5afb8ae9fc 100644
--- a/dom/payments/PaymentRequestUpdateEvent.h
+++ b/dom/payments/PaymentRequestUpdateEvent.h
@@ -8,12 +8,13 @@
 #define mozilla_dom_PaymentRequestUpdateEvent_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/Event.h"
 #include "mozilla/dom/PaymentRequestUpdateEventBinding.h"
 #include "mozilla/dom/PromiseNativeHandler.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Promise;
diff --git a/dom/plugins/base/nsPluginHost.cpp b/dom/plugins/base/nsPluginHost.cpp
index c74bb07b022f..4cc7d89e59d3 100644
--- a/dom/plugins/base/nsPluginHost.cpp
+++ b/dom/plugins/base/nsPluginHost.cpp
@@ -5,79 +5,106 @@
 
 /* nsPluginHost.cpp - top-level plugin management code */
 
-#include "nscore.h"
 #include "nsPluginHost.h"
 
-#include <cstdlib>
+#include <inttypes.h>
 #include <stdio.h>
-#include "nsComponentManagerUtils.h"
-#include "nsNPAPIPlugin.h"
-#include "nsNPAPIPluginStreamListener.h"
-#include "nsNPAPIPluginInstance.h"
-#include "nsPluginInstanceOwner.h"
-#include "nsObjectLoadingContent.h"
-#include "nsIEventTarget.h"
-#include "nsIObserverService.h"
-#include "nsIHttpProtocolHandler.h"
-#include "nsIHttpChannel.h"
-#include "nsIUploadChannel.h"
-#include "nsIStreamListener.h"
-#include "nsIInputStream.h"
-#include "nsTArray.h"
-#include "nsReadableUtils.h"
-#include "nsIFile.h"
-#include "nsISeekableStream.h"
-#include "nsNetUtil.h"
-#include "nsISimpleEnumerator.h"
-#include "nsIStringStream.h"
-#include "mozilla/dom/Document.h"
-#include "nsPluginLogging.h"
-#include "nsIScriptChannel.h"
-#include "nsIBlocklistService.h"
-#include "nsVersionComparator.h"
-#include "nsIObjectLoadingContent.h"
-#include "nsIWritablePropertyBag2.h"
-#include "nsICategoryManager.h"
-#include "nsPluginStreamListenerPeer.h"
-#include "mozilla/NullPrincipal.h"
-#include "mozilla/dom/ContentChild.h"
+#include <string.h>
+#include <cstdlib>
+#include <new>
+#include <utility>
+#include "GeckoProfiler.h"
+#include "ReferrerInfo.h"
+#include "js/RootingAPI.h"
+#include "mozilla/ArrayIterator.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MacroForEach.h"
+#include "mozilla/NotNull.h"
+#include "mozilla/PluginLibrary.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/TelemetryHistogramEnums.h"
+#include "mozilla/TextUtils.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/ContentParent.h"
+#include "mozilla/dom/Document.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/FakePluginTagInitBinding.h"
-#include "mozilla/ClearOnShutdown.h"
-#include "mozilla/LoadInfo.h"
-#include "mozilla/plugins/PluginBridge.h"
-#include "mozilla/plugins/PluginTypes.h"
-#include "mozilla/SpinEventLoopUntil.h"
-#include "mozilla/TextUtils.h"
-#include "mozilla/Preferences.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+#include "mozilla/dom/ReferrerPolicyBinding.h"
+#include "mozilla/fallible.h"
+#include "mozilla/ipc/URIParams.h"
 #include "mozilla/ipc/URIUtils.h"
-
-#include "nsEnumeratorUtils.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/plugins/PluginTypes.h"
+#include "npapi.h"
+#include "npfunctions.h"
+#include "nsComponentManagerUtils.h"
+#include "nsIAsyncShutdown.h"
+#include "nsIBlocklistService.h"
+#include "nsICategoryManager.h"
+#include "nsIChannel.h"
+#include "nsIContent.h"
+#include "nsIContentPolicy.h"
+#include "nsID.h"
+#include "nsIEffectiveTLDService.h"
+#include "nsIFile.h"
+#include "nsIHttpChannel.h"
+#include "nsIHttpProtocolHandler.h"
+#include "nsIIDNService.h"
+#include "nsIInputStream.h"
+#include "nsILoadInfo.h"
+#include "nsIObjectLoadingContent.h"
+#include "nsIObserverService.h"
+#include "nsIPluginInstanceOwner.h"
+#include "nsIPluginTag.h"
+#include "nsIPrefBranch.h"
+#include "nsIProtocolHandler.h"
+#include "nsIReferrerInfo.h"
+#include "nsIRequest.h"
+#include "nsIScriptChannel.h"
+#include "nsISeekableStream.h"
+#include "nsIStringStream.h"
+#include "nsISupportsUtils.h"
+#include "nsIURI.h"
+#include "nsIUploadChannel.h"
+#include "nsIWeakReference.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsIWritablePropertyBag2.h"
+#include "nsLiteralString.h"
+#include "nsNPAPIPlugin.h"
+#include "nsNPAPIPluginInstance.h"
+#include "nsNetCID.h"
+#include "nsNetUtil.h"
+#include "nsObjectLoadingContent.h"
+#include "nsPluginInstanceOwner.h"
+#include "nsPluginLogging.h"
+#include "nsPluginNativeWindow.h"
+#include "nsPluginStreamListenerPeer.h"
+#include "nsPluginTags.h"
+#include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "nsStringFlags.h"
+#include "nsTArray.h"
+#include "nsTLiteralString.h"
+#include "nsTPromiseFlatString.h"
+#include "nsTStringRepr.h"
+#include "nsThreadUtils.h"
+#include "nsVersionComparator.h"
 #include "nsXPCOM.h"
 #include "nsXPCOMCID.h"
-
 #include "nsXULAppAPI.h"
-
-// for the dialog
-
-#include "nsNetCID.h"
-#include "mozilla/Sprintf.h"
-#include "nsThreadUtils.h"
-#include "nsQueryObject.h"
-
-#include "nsIWeakReferenceUtils.h"
-#include "nsPluginNativeWindow.h"
-#include "nsIContentPolicy.h"
-#include "nsContentPolicyUtils.h"
-#include "mozilla/ResultExtensions.h"
-#include "mozilla/TimeStamp.h"
-#include "mozilla/Telemetry.h"
-#include "nsIImageLoadingContent.h"
-#include "nsVersionComparator.h"
-#include "ReferrerInfo.h"
-
-#include "mozilla/dom/Promise.h"
+#include "nscore.h"
+#include "plstr.h"
 
 #if defined(XP_WIN)
 #  include "nsIWindowMediator.h"
@@ -90,8 +117,6 @@
 #  include <gdk/gdkx.h>
 #endif
 
-#include "npapi.h"
-
 using namespace mozilla;
 using mozilla::TimeStamp;
 using mozilla::dom::Document;
diff --git a/dom/power/WakeLock.h b/dom/power/WakeLock.h
index 0174ceaa38d8..25038db8b10e 100644
--- a/dom/power/WakeLock.h
+++ b/dom/power/WakeLock.h
@@ -14,11 +14,12 @@
 #include "nsString.h"
 #include "nsWeakReference.h"
 #include "nsWrapperCache.h"
-#include "mozilla/ErrorResult.h"
 
 class nsPIDOMWindowInner;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class ContentParent;
diff --git a/dom/presentation/PresentationReceiver.h b/dom/presentation/PresentationReceiver.h
index eaae182ad044..b71cf0b8945d 100644
--- a/dom/presentation/PresentationReceiver.h
+++ b/dom/presentation/PresentationReceiver.h
@@ -7,7 +7,6 @@
 #ifndef mozilla_dom_PresentationReceiver_h
 #define mozilla_dom_PresentationReceiver_h
 
-#include "mozilla/ErrorResult.h"
 #include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsIPresentationListener.h"
@@ -17,6 +16,8 @@
 class nsPIDOMWindowInner;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class PresentationConnection;
diff --git a/dom/push/PushManager.h b/dom/push/PushManager.h
index 261e265f4473..fd2aa38e7dd0 100644
--- a/dom/push/PushManager.h
+++ b/dom/push/PushManager.h
@@ -29,7 +29,6 @@
 #include "nsWrapperCache.h"
 
 #include "mozilla/AlreadyAddRefed.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/TypedArray.h"
 
@@ -40,6 +39,8 @@ class nsIGlobalObject;
 class nsIPrincipal;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class OwningArrayBufferViewOrArrayBufferOrString;
diff --git a/dom/push/PushSubscription.h b/dom/push/PushSubscription.h
index bd09b0f4369d..ed8706eeff06 100644
--- a/dom/push/PushSubscription.h
+++ b/dom/push/PushSubscription.h
@@ -12,7 +12,6 @@
 #include "nsWrapperCache.h"
 
 #include "mozilla/AlreadyAddRefed.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 
 #include "mozilla/dom/BindingDeclarations.h"
@@ -23,6 +22,8 @@
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Promise;
diff --git a/dom/script/ScriptLoader.h b/dom/script/ScriptLoader.h
index bd3e0208c8ec..b1f23f28d36c 100644
--- a/dom/script/ScriptLoader.h
+++ b/dom/script/ScriptLoader.h
@@ -7,27 +7,30 @@
 #ifndef mozilla_dom_ScriptLoader_h
 #define mozilla_dom_ScriptLoader_h
 
+#include "js/TypeDecls.h"
 #include "nsCOMPtr.h"
 #include "nsRefPtrHashtable.h"
-#include "mozilla/Encoding.h"
 #include "nsIScriptElement.h"
 #include "nsCOMArray.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsTArray.h"
-#include "nsIIncrementalStreamLoader.h"
 #include "nsINode.h"
 #include "nsIObserver.h"
+#include "nsIScriptLoaderObserver.h"
 #include "nsURIHashKey.h"
 #include "mozilla/CORSMode.h"
+#include "mozilla/dom/LoadedScript.h"
 #include "mozilla/dom/ScriptLoadRequest.h"
-#include "mozilla/dom/SRIMetadata.h"
-#include "mozilla/dom/SRICheck.h"
 #include "mozilla/MaybeOneOf.h"
 #include "mozilla/MozPromise.h"
-#include "mozilla/Utf8.h"  // mozilla::Utf8Unit
-#include "mozilla/Vector.h"
 #include "ScriptKind.h"
 
+class nsCycleCollectionTraversalCallback;
+class nsIChannel;
+class nsIConsoleReportCollector;
+class nsIContent;
+class nsIIncrementalStreamLoader;
+class nsIPrincipal;
 class nsIScriptGlobalObject;
 class nsIURI;
 
@@ -39,17 +42,26 @@ class SourceText;
 }  // namespace JS
 
 namespace mozilla {
+
+class LazyLogModule;
+union Utf8Unit;
+
 namespace dom {
 
 class AutoJSAPI;
+class DocGroup;
 class Document;
 class LoadedScript;
 class ModuleLoadRequest;
 class ModuleScript;
+class SRICheckDataVerifier;
+class SRIMetadata;
 class ScriptLoadHandler;
 class ScriptLoader;
 class ScriptRequestProcessor;
 
+enum class ReferrerPolicy : uint8_t;
+
 class AsyncCompileShutdownObserver final : public nsIObserver {
   ~AsyncCompileShutdownObserver() { Unregister(); }
 
diff --git a/dom/storage/Storage.h b/dom/storage/Storage.h
index 5b659cd04afa..f197e1cb9d32 100644
--- a/dom/storage/Storage.h
+++ b/dom/storage/Storage.h
@@ -14,6 +14,8 @@
 #include "nsCOMPtr.h"
 #include "nsWrapperCache.h"
 #include "nsISupports.h"
+#include "nsTArrayForwardDeclare.h"
+#include "nsString.h"
 
 class nsIPrincipal;
 class nsPIDOMWindowInner;
diff --git a/dom/svg/DOMSVGLengthList.h b/dom/svg/DOMSVGLengthList.h
index 582d8945c48a..e488fa7286fb 100644
--- a/dom/svg/DOMSVGLengthList.h
+++ b/dom/svg/DOMSVGLengthList.h
@@ -14,7 +14,6 @@
 #include "nsTArray.h"
 #include "SVGLengthList.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Unused.h"
 
 // {cbecb7a4-d6f3-47b5-b5a3-3e5bdbf5b2f9}
@@ -26,6 +25,7 @@
   }
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 class DOMSVGLength;
diff --git a/dom/svg/DOMSVGNumber.h b/dom/svg/DOMSVGNumber.h
index 186981399189..08804f141372 100644
--- a/dom/svg/DOMSVGNumber.h
+++ b/dom/svg/DOMSVGNumber.h
@@ -12,13 +12,13 @@
 #include "nsCycleCollectionParticipant.h"
 #include "nsTArray.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 #include "nsWrapperCache.h"
 
 #define MOZ_SVG_LIST_INDEX_BIT_COUNT 27  // supports > 134 million list items
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 class SVGElement;
diff --git a/dom/svg/DOMSVGNumberList.h b/dom/svg/DOMSVGNumberList.h
index 68e7b92d4c87..b0fce39d5ca0 100644
--- a/dom/svg/DOMSVGNumberList.h
+++ b/dom/svg/DOMSVGNumberList.h
@@ -14,10 +14,10 @@
 #include "nsTArray.h"
 #include "SVGNumberList.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 class DOMSVGNumber;
diff --git a/dom/svg/DOMSVGPathSegList.h b/dom/svg/DOMSVGPathSegList.h
index 540df534269a..5fc833a9d28b 100644
--- a/dom/svg/DOMSVGPathSegList.h
+++ b/dom/svg/DOMSVGPathSegList.h
@@ -13,12 +13,12 @@
 #include "nsTArray.h"
 #include "SVGPathData.h"  // IWYU pragma: keep
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/dom/SVGElement.h"
 
 namespace mozilla {
 
+class ErrorResult;
 class SVGAnimatedPathSegList;
 
 namespace dom {
diff --git a/dom/svg/DOMSVGPointList.h b/dom/svg/DOMSVGPointList.h
index 364d43ebc0cd..2e5ad109c140 100644
--- a/dom/svg/DOMSVGPointList.h
+++ b/dom/svg/DOMSVGPointList.h
@@ -13,7 +13,6 @@
 #include "nsTArray.h"
 #include "SVGPointList.h"  // IWYU pragma: keep
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 
 // {61812ad1-c078-4cd1-87e6-bc1c1b8d7284}
@@ -26,6 +25,7 @@
 
 namespace mozilla {
 
+class ErrorResult;
 class SVGAnimatedPointList;
 
 namespace dom {
diff --git a/dom/svg/DOMSVGTransformList.h b/dom/svg/DOMSVGTransformList.h
index bb6dfabce04c..83776fe5f0f4 100644
--- a/dom/svg/DOMSVGTransformList.h
+++ b/dom/svg/DOMSVGTransformList.h
@@ -14,9 +14,9 @@
 #include "SVGTransformList.h"
 #include "nsTArray.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 struct DOMMatrix2DInit;
diff --git a/dom/svg/SVGAnimatedRect.h b/dom/svg/SVGAnimatedRect.h
index 09c5f34fd46a..ee43014c019c 100644
--- a/dom/svg/SVGAnimatedRect.h
+++ b/dom/svg/SVGAnimatedRect.h
@@ -10,7 +10,6 @@
 #include "nsCycleCollectionParticipant.h"
 #include "mozilla/dom/SVGElement.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
diff --git a/dom/svg/SVGPreserveAspectRatio.h b/dom/svg/SVGPreserveAspectRatio.h
index ce041dfcff7d..d591f6f36c9a 100644
--- a/dom/svg/SVGPreserveAspectRatio.h
+++ b/dom/svg/SVGPreserveAspectRatio.h
@@ -12,10 +12,10 @@
 
 #include "nsWrapperCache.h"
 #include "nsCycleCollectionParticipant.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/SVGElement.h"
 
 namespace mozilla {
+class ErrorResult;
 
 // These constants represent the range of valid enum values for the <align>
 // parameter. They exclude the sentinel _UNKNOWN value.
diff --git a/dom/system/PathUtils.h b/dom/system/PathUtils.h
index 62fe404bf60b..93ab77acd865 100644
--- a/dom/system/PathUtils.h
+++ b/dom/system/PathUtils.h
@@ -8,16 +8,17 @@
 #define mozilla_dom_PathUtils__
 
 #include "mozilla/DataMutex.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/MozPromise.h"
 #include "mozilla/Mutex.h"
-#include "mozilla/dom/DOMParser.h"
+#include "mozilla/Result.h"
 #include "mozilla/dom/Promise.h"
 #include "nsString.h"
 #include "nsTArray.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class PathUtils final {
diff --git a/dom/u2f/U2F.h b/dom/u2f/U2F.h
index a78841c21d3c..1e57e4bb22a6 100644
--- a/dom/u2f/U2F.h
+++ b/dom/u2f/U2F.h
@@ -13,7 +13,6 @@
 #include "mozilla/dom/Nullable.h"
 #include "mozilla/dom/U2FBinding.h"
 #include "mozilla/dom/WebAuthnManagerBase.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/MozPromise.h"
 #include "nsProxyRelease.h"
@@ -25,6 +24,8 @@
 #include "mozilla/dom/Document.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class WebAuthnMakeCredentialResult;
diff --git a/dom/vr/VRDisplay.h b/dom/vr/VRDisplay.h
index e37c2826cfda..1f4de0ee0cf0 100644
--- a/dom/vr/VRDisplay.h
+++ b/dom/vr/VRDisplay.h
@@ -9,7 +9,6 @@
 
 #include <stdint.h>
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/TypedArray.h"
 #include "mozilla/dom/VRDisplayBinding.h"
 #include "mozilla/DOMEventTargetHelper.h"
@@ -25,6 +24,8 @@
 #include "gfxVR.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace gfx {
 class VRDisplayClient;
 class VRDisplayPresentation;
diff --git a/dom/webauthn/AuthenticatorAssertionResponse.h b/dom/webauthn/AuthenticatorAssertionResponse.h
index 19931a735cb7..899b1369b112 100644
--- a/dom/webauthn/AuthenticatorAssertionResponse.h
+++ b/dom/webauthn/AuthenticatorAssertionResponse.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/AuthenticatorResponse.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/CryptoBuffer.h"
diff --git a/dom/webauthn/AuthenticatorAttestationResponse.h b/dom/webauthn/AuthenticatorAttestationResponse.h
index 896915729d54..45f96c702667 100644
--- a/dom/webauthn/AuthenticatorAttestationResponse.h
+++ b/dom/webauthn/AuthenticatorAttestationResponse.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/AuthenticatorResponse.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/CryptoBuffer.h"
diff --git a/dom/webauthn/AuthenticatorResponse.h b/dom/webauthn/AuthenticatorResponse.h
index 821365d16593..195ec181ac08 100644
--- a/dom/webauthn/AuthenticatorResponse.h
+++ b/dom/webauthn/AuthenticatorResponse.h
@@ -9,7 +9,6 @@
 
 #include "js/TypeDecls.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/CryptoBuffer.h"
 #include "nsCycleCollectionParticipant.h"
diff --git a/dom/webauthn/PublicKeyCredential.h b/dom/webauthn/PublicKeyCredential.h
index da7c98de7866..ffdb2b055e30 100644
--- a/dom/webauthn/PublicKeyCredential.h
+++ b/dom/webauthn/PublicKeyCredential.h
@@ -11,7 +11,6 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/Credential.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "mozilla/dom/CryptoBuffer.h"
diff --git a/dom/websocket/WebSocket.h b/dom/websocket/WebSocket.h
index 563b48834168..52e55361cf5f 100644
--- a/dom/websocket/WebSocket.h
+++ b/dom/websocket/WebSocket.h
@@ -12,7 +12,6 @@
 #include "mozilla/dom/TypedArray.h"
 #include "mozilla/dom/WebSocketBinding.h"  // for BinaryType
 #include "mozilla/DOMEventTargetHelper.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Mutex.h"
 #include "nsCOMPtr.h"
 #include "nsCycleCollectionParticipant.h"
@@ -28,6 +27,8 @@ class nsIInputStream;
 class nsITransportProvider;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class Blob;
diff --git a/dom/workers/WorkerNavigator.h b/dom/workers/WorkerNavigator.h
index c6a9f7cd2bae..df8206254948 100644
--- a/dom/workers/WorkerNavigator.h
+++ b/dom/workers/WorkerNavigator.h
@@ -11,7 +11,6 @@
 #include "js/RootingAPI.h"
 #include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Assertions.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/workerinternals/RuntimeService.h"
@@ -22,6 +21,8 @@
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace webgpu {
 class Instance;
 }  // namespace webgpu
diff --git a/dom/workers/WorkerScope.h b/dom/workers/WorkerScope.h
index 9eb5fe1e8a8c..daf13a15dff1 100644
--- a/dom/workers/WorkerScope.h
+++ b/dom/workers/WorkerScope.h
@@ -10,7 +10,6 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/DOMEventTargetHelper.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/NotNull.h"
 #include "mozilla/RefPtr.h"
@@ -37,6 +36,8 @@ class nsAtom;
 class nsISerialEventTarget;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class AnyCallback;
diff --git a/dom/worklet/Worklet.h b/dom/worklet/Worklet.h
index a0e1f8058cea..5d7627428f43 100644
--- a/dom/worklet/Worklet.h
+++ b/dom/worklet/Worklet.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_Worklet_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsRefPtrHashtable.h"
 #include "nsWrapperCache.h"
 #include "nsCOMPtr.h"
@@ -17,6 +16,7 @@ class nsPIDOMWindowInner;
 
 namespace mozilla {
 
+class ErrorResult;
 class WorkletImpl;
 
 namespace dom {
diff --git a/dom/worklet/WorkletGlobalScope.h b/dom/worklet/WorkletGlobalScope.h
index 338b454c0000..3f24415d424b 100644
--- a/dom/worklet/WorkletGlobalScope.h
+++ b/dom/worklet/WorkletGlobalScope.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_WorkletGlobalScope_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/dom/BindingDeclarations.h"
@@ -25,6 +24,7 @@
 
 namespace mozilla {
 
+class ErrorResult;
 class WorkletImpl;
 
 namespace dom {
diff --git a/dom/xslt/xpath/XPathEvaluator.h b/dom/xslt/xpath/XPathEvaluator.h
index d661c5d82dee..7401d9321440 100644
--- a/dom/xslt/xpath/XPathEvaluator.h
+++ b/dom/xslt/xpath/XPathEvaluator.h
@@ -9,7 +9,6 @@
 #include "mozilla/dom/NonRefcountedDOMObject.h"
 #include "nsString.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/Document.h"
 
 class nsINode;
@@ -17,6 +16,8 @@ class txIParseContext;
 class txResultRecycler;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class GlobalObject;
diff --git a/dom/xslt/xslt/txMozillaXSLTProcessor.h b/dom/xslt/xslt/txMozillaXSLTProcessor.h
index 7582c7333f4b..a02877b175a4 100644
--- a/dom/xslt/xslt/txMozillaXSLTProcessor.h
+++ b/dom/xslt/xslt/txMozillaXSLTProcessor.h
@@ -13,7 +13,6 @@
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/ReferrerPolicyBinding.h"
 #include "mozilla/dom/XSLTProcessorBinding.h"
@@ -26,6 +25,8 @@ class txResultRecycler;
 class txIGlobalParameter;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class DocGroup;
diff --git a/dom/xul/XULFrameElement.h b/dom/xul/XULFrameElement.h
index 251b2195e1c5..72247c7f0684 100644
--- a/dom/xul/XULFrameElement.h
+++ b/dom/xul/XULFrameElement.h
@@ -8,7 +8,6 @@
 #define XULFrameElement_h__
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/Nullable.h"
 #include "mozilla/dom/WindowProxyHolder.h"
 #include "js/TypeDecls.h"
@@ -23,6 +22,8 @@ class nsIWebNavigation;
 class nsFrameLoader;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class BrowsingContext;
diff --git a/dom/xul/XULPopupElement.h b/dom/xul/XULPopupElement.h
index ac5065c88afb..825a69be4049 100644
--- a/dom/xul/XULPopupElement.h
+++ b/dom/xul/XULPopupElement.h
@@ -8,7 +8,6 @@
 #define XULPopupElement_h__
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "nsString.h"
@@ -17,6 +16,8 @@
 struct JSContext;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class DOMRect;
diff --git a/dom/xul/XULTreeElement.h b/dom/xul/XULTreeElement.h
index 78e4926986c0..f80f7cbb51e2 100644
--- a/dom/xul/XULTreeElement.h
+++ b/dom/xul/XULTreeElement.h
@@ -8,7 +8,6 @@
 #define XULTreeElement_h__
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "nsString.h"
@@ -20,6 +19,8 @@ class nsTreeColumn;
 class nsTreeColumns;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 struct TreeCellInfo;
diff --git a/editor/libeditor/ReplaceTextTransaction.h b/editor/libeditor/ReplaceTextTransaction.h
index 17651fb68f15..d07bbf018f49 100644
--- a/editor/libeditor/ReplaceTextTransaction.h
+++ b/editor/libeditor/ReplaceTextTransaction.h
@@ -10,7 +10,6 @@
 #include "mozilla/EditorBase.h"
 #include "mozilla/EditorDOMPoint.h"
 #include "mozilla/EditTransactionBase.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/dom/Text.h"
diff --git a/gfx/2d/BezierUtils.h b/gfx/2d/BezierUtils.h
index 2a315380c46f..3ffcd7021452 100644
--- a/gfx/2d/BezierUtils.h
+++ b/gfx/2d/BezierUtils.h
@@ -7,8 +7,8 @@
 #ifndef mozilla_BezierUtils_h_
 #define mozilla_BezierUtils_h_
 
-#include "mozilla/gfx/2D.h"
-#include "gfxRect.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/gfx/Types.h"
 
 namespace mozilla {
 namespace gfx {
diff --git a/gfx/2d/RecordedEvent.h b/gfx/2d/RecordedEvent.h
index 4b68798dd69c..4bbd72e05f92 100644
--- a/gfx/2d/RecordedEvent.h
+++ b/gfx/2d/RecordedEvent.h
@@ -7,7 +7,6 @@
 #ifndef MOZILLA_GFX_RECORDEDEVENT_H_
 #define MOZILLA_GFX_RECORDEDEVENT_H_
 
-#include "2D.h"
 #include <ostream>
 #include <sstream>
 #include <cstring>
@@ -15,6 +14,8 @@
 #include <vector>
 
 #include "RecordingTypes.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/gfx/Types.h"
 #include "mozilla/ipc/ByteBuf.h"
 
 namespace mozilla {
diff --git a/gfx/gl/GLScreenBuffer.h b/gfx/gl/GLScreenBuffer.h
index f796e1568a7e..17a4bd9c2f8c 100644
--- a/gfx/gl/GLScreenBuffer.h
+++ b/gfx/gl/GLScreenBuffer.h
@@ -15,12 +15,9 @@
 #ifndef SCREEN_BUFFER_H_
 #define SCREEN_BUFFER_H_
 
-#include "GLContextTypes.h"
-#include "GLDefs.h"
-#include "mozilla/gfx/2D.h"
+#include "GLTypes.h"
 #include "mozilla/gfx/Point.h"
 #include "mozilla/UniquePtr.h"
-#include "SurfaceTypes.h"
 
 #include <queue>
 #include <memory>
diff --git a/gfx/ipc/CrossProcessPaint.h b/gfx/ipc/CrossProcessPaint.h
index 531589c104eb..eb7907d59b32 100644
--- a/gfx/ipc/CrossProcessPaint.h
+++ b/gfx/ipc/CrossProcessPaint.h
@@ -9,10 +9,9 @@
 #include "nsISupportsImpl.h"
 
 #include "mozilla/dom/ipc/IdType.h"
-#include "mozilla/dom/Promise.h"
-#include "mozilla/dom/DOMRect.h"
-#include "mozilla/gfx/2D.h"
-#include "mozilla/Maybe.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/gfx/RecordedEvent.h"
+#include "mozilla/gfx/Rect.h"
 #include "mozilla/MozPromise.h"
 #include "mozilla/ipc/ByteBuf.h"
 #include "nsColor.h"
@@ -20,7 +19,8 @@
 #include "nsHashKeys.h"
 #include "nsRefPtrHashtable.h"
 #include "nsTHashtable.h"
-#include "mozilla/gfx/RecordedEvent.h"
+
+class nsIDocShell;
 
 namespace IPC {
 template <typename T>
@@ -30,6 +30,8 @@ struct ParamTraits;
 namespace mozilla {
 
 namespace dom {
+class DOMRect;
+class Promise;
 class WindowGlobalParent;
 }  // namespace dom
 
diff --git a/gfx/layers/Effects.h b/gfx/layers/Effects.h
index 2698e9de2ee4..b138fefcc76e 100644
--- a/gfx/layers/Effects.h
+++ b/gfx/layers/Effects.h
@@ -14,10 +14,9 @@
 #include "mozilla/gfx/Rect.h"    // for Rect
 #include "mozilla/gfx/Types.h"   // for SamplingFilter, etc
 #include "mozilla/layers/CompositorTypes.h"  // for EffectTypes, etc
-#include "mozilla/layers/LayersTypes.h"
-#include "mozilla/layers/TextureHost.h"  // for CompositingRenderTarget, etc
-#include "mozilla/mozalloc.h"            // for operator delete, etc
-#include "nscore.h"                      // for nsACString
+#include "mozilla/layers/TextureHost.h"      // for CompositingRenderTarget, etc
+#include "mozilla/mozalloc.h"                // for operator delete, etc
+#include "nscore.h"                          // for nsACString
 #include "mozilla/EnumeratedArray.h"
 
 namespace mozilla {
diff --git a/gfx/layers/ImageContainer.h b/gfx/layers/ImageContainer.h
index 6f4a3818fece..66fd6d193eea 100644
--- a/gfx/layers/ImageContainer.h
+++ b/gfx/layers/ImageContainer.h
@@ -7,28 +7,24 @@
 #ifndef GFX_IMAGECONTAINER_H
 #define GFX_IMAGECONTAINER_H
 
-#include <stdint.h>     // for uint32_t, uint8_t, uint64_t
-#include <sys/types.h>  // for int32_t
-#include "gfxTypes.h"
-#include "ImageTypes.h"              // for ImageFormat, etc
+#include <stdint.h>      // for int32_t, uint32_t, uint8_t, uint64_t
+#include "ImageTypes.h"  // for ImageFormat, etc
+#include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Assertions.h"      // for MOZ_ASSERT_HELPER2
 #include "mozilla/Mutex.h"           // for Mutex
 #include "mozilla/RecursiveMutex.h"  // for RecursiveMutex, etc
 #include "mozilla/ThreadSafeWeakPtr.h"
-#include "mozilla/TimeStamp.h"           // for TimeStamp
-#include "mozilla/gfx/Point.h"           // For IntSize
+#include "mozilla/TimeStamp.h"  // for TimeStamp
+#include "mozilla/gfx/Point.h"  // For IntSize
+#include "mozilla/gfx/Rect.h"
 #include "mozilla/gfx/Types.h"           // For ColorDepth
 #include "mozilla/layers/LayersTypes.h"  // for LayersBackend, etc
 #include "mozilla/layers/CompositorTypes.h"
 #include "mozilla/mozalloc.h"  // for operator delete, etc
-#include "nsCOMPtr.h"          // for already_AddRefed
 #include "nsDebug.h"           // for NS_ASSERTION
 #include "nsISupportsImpl.h"   // for Image::Release, etc
-#include "nsRect.h"            // for mozilla::gfx::IntRect
 #include "nsTArray.h"          // for nsTArray
 #include "mozilla/Atomics.h"
-#include "mozilla/WeakPtr.h"
-#include "nsThreadUtils.h"
 #include "mozilla/gfx/2D.h"
 #include "nsDataHashtable.h"
 #include "mozilla/EnumeratedArray.h"
diff --git a/gfx/layers/RotatedBuffer.h b/gfx/layers/RotatedBuffer.h
index eaaa152e2214..ceda001b031a 100644
--- a/gfx/layers/RotatedBuffer.h
+++ b/gfx/layers/RotatedBuffer.h
@@ -9,16 +9,15 @@
 
 #include "gfxTypes.h"
 #include <stdint.h>                        // for uint32_t
+#include "mozilla/AlreadyAddRefed.h"       // for already_AddRefed
 #include "mozilla/Assertions.h"            // for MOZ_ASSERT, etc
 #include "mozilla/RefPtr.h"                // for RefPtr, already_AddRefed
 #include "mozilla/gfx/2D.h"                // for DrawTarget, etc
 #include "mozilla/gfx/MatrixFwd.h"         // for Matrix
 #include "mozilla/layers/TextureClient.h"  // for TextureClient
 #include "mozilla/mozalloc.h"              // for operator delete
-#include "nsCOMPtr.h"                      // for already_AddRefed
 #include "nsISupportsImpl.h"               // for MOZ_COUNT_CTOR, etc
 #include "nsRegion.h"                      // for nsIntRegion
-#include "LayersTypes.h"
 
 namespace mozilla {
 namespace layers {
diff --git a/gfx/layers/apz/public/APZPublicUtils.h b/gfx/layers/apz/public/APZPublicUtils.h
index b24130d2ea77..671f3186f4fe 100644
--- a/gfx/layers/apz/public/APZPublicUtils.h
+++ b/gfx/layers/apz/public/APZPublicUtils.h
@@ -10,25 +10,20 @@
 // This file is for APZ-related utilities that need to be consumed from outside
 // of gfx/layers. For internal utilities, prefer APZUtils.h.
 
-#include <stdint.h>  // for uint32_t
-#include <type_traits>
+#include <stdint.h>
 #include <utility>
-#include "gfxTypes.h"
-#include "FrameMetrics.h"
-#include "LayersTypes.h"
-#include "UnitTransforms.h"
-#include "mozilla/gfx/CompositorHitTestInfo.h"
-#include "mozilla/gfx/Point.h"
-#include "mozilla/DefineEnum.h"
-#include "mozilla/EnumSet.h"
-#include "mozilla/FloatingPoint.h"
-#include "mozilla/ScrollOrigin.h"
 #include "ScrollAnimationBezierPhysics.h"
+#include "Units.h"
+#include "mozilla/DefineEnum.h"
+#include "mozilla/ScrollOrigin.h"
+#include "mozilla/gfx/Point.h"
 
 namespace mozilla {
 
 namespace layers {
 
+struct FrameMetrics;
+
 // clang-format off
 MOZ_DEFINE_ENUM_CLASS_WITH_BASE(APZWheelAction, uint8_t, (
     Scroll,
diff --git a/gfx/layers/apz/util/CheckerboardReportService.h b/gfx/layers/apz/util/CheckerboardReportService.h
index ff3da310c258..3062255f95bc 100644
--- a/gfx/layers/apz/util/CheckerboardReportService.h
+++ b/gfx/layers/apz/util/CheckerboardReportService.h
@@ -10,7 +10,6 @@
 #include <string>
 
 #include "js/TypeDecls.h"            // for JSContext, JSObject
-#include "mozilla/ErrorResult.h"     // for ErrorResult
 #include "mozilla/StaticPtr.h"       // for StaticRefPtr
 #include "nsCOMPtr.h"                // for nsCOMPtr
 #include "nsISupports.h"             // for NS_INLINE_DECL_REFCOUNTING
diff --git a/gfx/layers/composite/TextureHost.h b/gfx/layers/composite/TextureHost.h
index 84c8e6e6f392..f6e7a3fa1fb8 100644
--- a/gfx/layers/composite/TextureHost.h
+++ b/gfx/layers/composite/TextureHost.h
@@ -7,18 +7,17 @@
 #ifndef MOZILLA_GFX_TEXTUREHOST_H
 #define MOZILLA_GFX_TEXTUREHOST_H
 
-#include <functional>
-#include <stddef.h>  // for size_t
-#include <stdint.h>  // for uint64_t, uint32_t, uint8_t
-#include "gfxTypes.h"
+#include <stddef.h>              // for size_t
+#include <stdint.h>              // for uint64_t, uint32_t, uint8_t
 #include "mozilla/Assertions.h"  // for MOZ_ASSERT, etc
 #include "mozilla/Attributes.h"  // for override
 #include "mozilla/RefPtr.h"      // for RefPtr, already_AddRefed, etc
-#include "mozilla/gfx/2D.h"      // for DataSourceSurface
-#include "mozilla/gfx/Point.h"   // for IntSize, IntPoint
-#include "mozilla/gfx/Types.h"   // for SurfaceFormat, etc
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/gfx/Matrix.h"
+#include "mozilla/gfx/Point.h"  // for IntSize, IntPoint
+#include "mozilla/gfx/Rect.h"
+#include "mozilla/gfx/Types.h"  // for SurfaceFormat, etc
 #include "mozilla/ipc/FileDescriptor.h"
-#include "mozilla/layers/Compositor.h"       // for Compositor
 #include "mozilla/layers/CompositorTypes.h"  // for TextureFlags, etc
 #include "mozilla/layers/LayersTypes.h"      // for LayerRenderState, etc
 #include "mozilla/layers/LayersSurfaces.h"
@@ -29,14 +28,18 @@
 #include "nsCOMPtr.h"         // for already_AddRefed
 #include "nsDebug.h"          // for NS_WARNING
 #include "nsISupportsImpl.h"  // for MOZ_COUNT_CTOR, etc
-#include "nsRegion.h"         // for nsIntRegion
-#include "nsTraceRefcnt.h"    // for MOZ_COUNT_CTOR, etc
-#include "nscore.h"           // for nsACString
+#include "nsRect.h"
+#include "nsRegion.h"       // for nsIntRegion
+#include "nsTraceRefcnt.h"  // for MOZ_COUNT_CTOR, etc
+#include "nscore.h"         // for nsACString
 #include "mozilla/layers/AtomicRefCountedWithFinalize.h"
-#include "mozilla/gfx/Rect.h"
 
 class MacIOSurface;
 namespace mozilla {
+namespace gfx {
+class DataSourceSurface;
+}
+
 namespace ipc {
 class Shmem;
 }  // namespace ipc
@@ -66,6 +69,7 @@ class TextureReadLock;
 class TextureSourceOGL;
 class TextureSourceD3D11;
 class TextureSourceBasic;
+class TextureSourceProvider;
 class DataTextureSource;
 class PTextureParent;
 class TextureParent;
diff --git a/gfx/layers/ipc/ISurfaceAllocator.h b/gfx/layers/ipc/ISurfaceAllocator.h
index 736a33a15fc6..740c3b2b3ede 100644
--- a/gfx/layers/ipc/ISurfaceAllocator.h
+++ b/gfx/layers/ipc/ISurfaceAllocator.h
@@ -16,7 +16,6 @@
 #include "nsIMemoryReporter.h"              // for nsIMemoryReporter
 #include "mozilla/Atomics.h"                // for Atomic
 #include "mozilla/layers/LayersMessages.h"  // for ShmemSection
-#include "LayersTypes.h"
 
 namespace mozilla {
 namespace ipc {
diff --git a/gfx/src/nsColor.h b/gfx/src/nsColor.h
index 5e850c7f9ae3..e47f5a4575c7 100644
--- a/gfx/src/nsColor.h
+++ b/gfx/src/nsColor.h
@@ -7,9 +7,7 @@
 #ifndef nsColor_h___
 #define nsColor_h___
 
-#include <stddef.h>   // for size_t
 #include <stdint.h>   // for uint8_t, uint32_t
-#include "nscore.h"   // for nsAString
 #include "nsCoord.h"  // for NSToIntRound
 #include "nsStringFwd.h"
 
diff --git a/gfx/src/nsCoord.h b/gfx/src/nsCoord.h
index 00fa802c3be9..fe90127411d2 100644
--- a/gfx/src/nsCoord.h
+++ b/gfx/src/nsCoord.h
@@ -7,17 +7,13 @@
 #ifndef NSCOORD_H
 #define NSCOORD_H
 
-#include "mozilla/FloatingPoint.h"
-
-#include "nsAlgorithm.h"
-#include "nscore.h"
-#include "nsMathUtils.h"
-#include <math.h>
-#include <float.h>
-#include <stdlib.h>
-
-#include "nsDebug.h"
 #include <algorithm>
+#include <cstdint>
+#include <cstdlib>
+#include <math.h>
+
+#include "mozilla/Assertions.h"
+#include "nsMathUtils.h"
 
 /*
  * Basic type used for the geometry classes.
diff --git a/gfx/src/nsFont.h b/gfx/src/nsFont.h
index 9a454a3064e6..9217aeab104b 100644
--- a/gfx/src/nsFont.h
+++ b/gfx/src/nsFont.h
@@ -7,19 +7,16 @@
 #ifndef nsFont_h___
 #define nsFont_h___
 
-#include <stdint.h>     // for uint8_t, uint16_t
-#include <sys/types.h>  // for int16_t
+#include <cstdint>
 #include "gfxFontFamilyList.h"
 #include "gfxFontConstants.h"  // for NS_FONT_KERNING_AUTO, etc
-#include "gfxFontFeatures.h"
 #include "gfxFontVariations.h"
 #include "mozilla/FontPropertyTypes.h"
-#include "mozilla/RefPtr.h"  // for RefPtr
 #include "mozilla/ServoStyleConstsInlines.h"
 #include "mozilla/StyleColorInlines.h"  // for StyleRGBA
-#include "nsCoord.h"                    // for nscoord
 #include "nsTArray.h"                   // for nsTArray
 
+struct gfxFontFeature;
 struct gfxFontStyle;
 
 // Font structure.
diff --git a/gfx/src/nsFontMetrics.h b/gfx/src/nsFontMetrics.h
index b2f9554a0aef..c98dac005177 100644
--- a/gfx/src/nsFontMetrics.h
+++ b/gfx/src/nsFontMetrics.h
@@ -15,7 +15,8 @@
 #include "nsError.h"             // for nsresult
 #include "nsFont.h"              // for nsFont
 #include "nsISupports.h"         // for NS_INLINE_DECL_REFCOUNTING
-#include "nscore.h"              // for char16_t
+#include "nsStyleConsts.h"
+#include "nscore.h"  // for char16_t
 
 class gfxContext;
 class gfxFontGroup;
diff --git a/gfx/src/nsITheme.h b/gfx/src/nsITheme.h
index 1208d77c1a17..fdda5e3b5a90 100644
--- a/gfx/src/nsITheme.h
+++ b/gfx/src/nsITheme.h
@@ -9,9 +9,10 @@
 #ifndef nsITheme_h_
 #define nsITheme_h_
 
+#include "mozilla/AlreadyAddRefed.h"
 #include "nsISupports.h"
-#include "nsCOMPtr.h"
-#include "nsColor.h"
+#include "nsID.h"
+#include "nscore.h"
 #include "Units.h"
 
 struct nsRect;
diff --git a/gfx/src/nsMargin.h b/gfx/src/nsMargin.h
index 7659693bcbc8..cf05894ff375 100644
--- a/gfx/src/nsMargin.h
+++ b/gfx/src/nsMargin.h
@@ -8,7 +8,6 @@
 #define NSMARGIN_H
 
 #include "nsCoord.h"
-#include "nsPoint.h"
 #include "mozilla/gfx/BaseMargin.h"
 #include "mozilla/gfx/Rect.h"
 
diff --git a/gfx/src/nsPoint.h b/gfx/src/nsPoint.h
index 9d2932afebc4..86688d214240 100644
--- a/gfx/src/nsPoint.h
+++ b/gfx/src/nsPoint.h
@@ -7,10 +7,9 @@
 #ifndef NSPOINT_H
 #define NSPOINT_H
 
+#include <cstdint>
 #include "nsCoord.h"
-#include "mozilla/gfx/BaseSize.h"
 #include "mozilla/gfx/BasePoint.h"
-#include "nsSize.h"
 #include "mozilla/gfx/Point.h"
 
 // nsIntPoint represents a point in one of the types of pixels.
diff --git a/gfx/src/nsRect.h b/gfx/src/nsRect.h
index 53982e57a179..4119b7b83d55 100644
--- a/gfx/src/nsRect.h
+++ b/gfx/src/nsRect.h
@@ -7,19 +7,15 @@
 #ifndef NSRECT_H
 #define NSRECT_H
 
-#include <stdio.h>           // for FILE
 #include <stdint.h>          // for int32_t, int64_t
 #include <algorithm>         // for min/max
 #include "mozilla/Likely.h"  // for MOZ_UNLIKELY
+#include "mozilla/gfx/BaseRect.h"
 #include "mozilla/gfx/Rect.h"
-#include "mozilla/gfx/2D.h"
-#include "mozilla/gfx/Logging.h"
-#include "nsCoord.h"          // for nscoord, etc
-#include "nsISupportsImpl.h"  // for MOZ_COUNT_CTOR, etc
-#include "nsPoint.h"          // for nsIntPoint, nsPoint
-#include "nsMargin.h"         // for nsIntMargin, nsMargin
-#include "nsSize.h"           // for IntSize, nsSize
-#include "nscore.h"           // for NS_BUILD_REFCNT_LOGGING
+#include "nsCoord.h"      // for nscoord, etc
+#include "nsISupports.h"  // for MOZ_COUNT_CTOR, etc
+#include "nsPoint.h"      // for nsIntPoint, nsPoint
+#include "nsSize.h"       // for IntSize, nsSize
 #if !defined(ANDROID) && (defined(__SSE2__) || defined(_M_X64) || \
                           (defined(_M_IX86_FP) && _M_IX86_FP >= 2))
 #  if defined(_MSC_VER) && !defined(__clang__)
@@ -29,6 +25,8 @@
 #  endif
 #endif
 
+struct nsMargin;
+
 typedef mozilla::gfx::IntRect nsIntRect;
 
 struct nsRect : public mozilla::gfx::BaseRect<nscoord, nsRect, nsPoint, nsSize,
diff --git a/gfx/src/nsRectAbsolute.h b/gfx/src/nsRectAbsolute.h
index 3971d7a5cc84..2ebedbffd7e3 100644
--- a/gfx/src/nsRectAbsolute.h
+++ b/gfx/src/nsRectAbsolute.h
@@ -9,7 +9,7 @@
 
 #include "mozilla/gfx/RectAbsolute.h"
 #include "nsCoord.h"
-#include "nsPoint.h"
+#include "nsMargin.h"
 #include "nsRect.h"
 
 struct nsRectAbsolute
diff --git a/gfx/src/nsRegion.h b/gfx/src/nsRegion.h
index 2aac56c13174..9c0fd8ed0063 100644
--- a/gfx/src/nsRegion.h
+++ b/gfx/src/nsRegion.h
@@ -7,18 +7,15 @@
 #ifndef nsRegion_h__
 #define nsRegion_h__
 
-#include <stddef.h>     // for size_t
-#include <stdint.h>     // for uint32_t, uint64_t
-#include <sys/types.h>  // for int32_t
+#include <stddef.h>  // for size_t
+#include <stdint.h>  // for uint32_t, uint64_t
 
 #include <ostream>  // for std::ostream
 #include <utility>  // for mozilla::Move
 
-#include "mozilla/ArrayView.h"  // for ArrayView
-#include "mozilla/gfx/Logging.h"
+#include "mozilla/ArrayView.h"      // for ArrayView
 #include "mozilla/gfx/MatrixFwd.h"  // for mozilla::gfx::Matrix4x4
 #include "nsCoord.h"                // for nscoord
-#include "nsError.h"                // for nsresult
 #include "nsMargin.h"               // for nsIntMargin
 #include "nsPoint.h"                // for nsIntPoint, nsPoint
 #include "nsRect.h"                 // for mozilla::gfx::IntRect, nsRect
diff --git a/gfx/thebes/gfx2DGlue.h b/gfx/thebes/gfx2DGlue.h
index 41342bff1ba6..578d7425026e 100644
--- a/gfx/thebes/gfx2DGlue.h
+++ b/gfx/thebes/gfx2DGlue.h
@@ -12,8 +12,9 @@
 #include "gfxRect.h"
 #include "gfxTypes.h"
 #include "mozilla/gfx/Matrix.h"
+#include "mozilla/gfx/Point.h"
 #include "mozilla/gfx/Rect.h"
-#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Types.h"
 
 namespace mozilla {
 namespace gfx {
diff --git a/gfx/thebes/gfxFont.h b/gfx/thebes/gfxFont.h
index 636883e8a4ee..2d4b7be96f45 100644
--- a/gfx/thebes/gfxFont.h
+++ b/gfx/thebes/gfxFont.h
@@ -7,46 +7,76 @@
 #ifndef GFX_FONT_H
 #define GFX_FONT_H
 
+#include <new>
+#include <utility>
+#include "PLDHashTable.h"
+#include "ThebesRLBoxTypes.h"
+#include "gfxFontVariations.h"
+#include "gfxRect.h"
 #include "gfxTypes.h"
-#include "gfxFontEntry.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/FontPropertyTypes.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ServoStyleConsts.h"
+#include "mozilla/TypedEnumBits.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/gfx/MatrixFwd.h"
+#include "mozilla/gfx/Point.h"
+#include "nsCOMPtr.h"
+#include "nsColor.h"
+#include "nsDataHashtable.h"
+#include "nsExpirationTracker.h"
+#include "nsFontMetrics.h"
+#include "nsHashKeys.h"
+#include "nsIMemoryReporter.h"
+#include "nsIObserver.h"
+#include "nsISupports.h"
 #include "nsString.h"
 #include "nsTArray.h"
 #include "nsTHashtable.h"
-#include "nsHashKeys.h"
-#include "gfxRect.h"
-#include "nsExpirationTracker.h"
+#include "nsUnicodeScriptCodes.h"
+#include "nscore.h"
+
+// Only required for function bodys
+#include <stdlib.h>
+#include <string.h>
+#include <algorithm>
+#include "mozilla/Assertions.h"
+#include "mozilla/HashFunctions.h"
+#include "mozilla/ServoUtils.h"
+#include "mozilla/gfx/2D.h"
+#include "gfxFontEntry.h"
+#include "gfxFontFeatures.h"
+#include "gfxFontUtils.h"
 #include "gfxPlatform.h"
 #include "nsAtom.h"
-#include "mozilla/HashFunctions.h"
-#include "nsIMemoryReporter.h"
-#include "nsIObserver.h"
-#include "mozilla/MemoryReporting.h"
-#include "mozilla/Attributes.h"
-#include "mozilla/FontPropertyTypes.h"
-#include "mozilla/TypedEnumBits.h"
-#include <algorithm>
-#include "DrawMode.h"
-#include "nsDataHashtable.h"
-#include "mozilla/gfx/2D.h"
-#include "nsColor.h"
-#include "nsFontMetrics.h"
-#include "mozilla/ServoUtils.h"
-#include "ThebesRLBoxTypes.h"
+#include "nsDebug.h"
+#include "nsMathUtils.h"
 
-typedef struct _cairo cairo_t;
-typedef struct _cairo_scaled_font cairo_scaled_font_t;
-
-#ifdef DEBUG
-#  include <stdio.h>
-#endif
-
-class gfxTextRun;
+class gfxContext;
 class gfxGlyphExtents;
+class gfxMathTable;
 class gfxPattern;
 class gfxShapedText;
 class gfxShapedWord;
 class gfxSkipChars;
-class gfxMathTable;
+class gfxTextRun;
+class nsIEventTarget;
+class nsITimer;
+struct gfxTextRunDrawCallbacks;
+enum class DrawMode : int;
+
+namespace mozilla {
+class SVGContextPaint;
+namespace layout {
+class TextDrawTarget;
+}
+}  // namespace mozilla
+
+typedef struct _cairo cairo_t;
+typedef struct _cairo_scaled_font cairo_scaled_font_t;
 
 #define FONT_MAX_SIZE 2000.0
 
@@ -62,16 +92,6 @@ class gfxMathTable;
 #  define OBLIQUE_SKEW_FACTOR 0.25f
 #endif
 
-struct gfxTextRunDrawCallbacks;
-
-namespace mozilla {
-class SVGContextPaint;
-
-namespace layout {
-class TextDrawTarget;
-}
-}  // namespace mozilla
-
 struct gfxFontStyle {
   typedef mozilla::FontStretch FontStretch;
   typedef mozilla::FontSlantStyle FontSlantStyle;
diff --git a/gfx/thebes/gfxFontEntry.h b/gfx/thebes/gfxFontEntry.h
index 1d69025be0d4..6ab6f08d7f35 100644
--- a/gfx/thebes/gfxFontEntry.h
+++ b/gfx/thebes/gfxFontEntry.h
@@ -6,54 +6,63 @@
 #ifndef GFX_FONTENTRY_H
 #define GFX_FONTENTRY_H
 
-#include "gfxTypes.h"
-#include "nsString.h"
-#include "gfxFontConstants.h"
-#include "gfxFontFeatures.h"
+#include <math.h>
+#include <new>
+#include <utility>
+#include "ThebesRLBoxTypes.h"
 #include "gfxFontUtils.h"
 #include "gfxFontVariations.h"
-#include "gfxPlatform.h"
 #include "gfxRect.h"
-#include "nsTArray.h"
-#include "nsTHashtable.h"
-#include "mozilla/HashFunctions.h"
-#include "mozilla/MemoryReporting.h"
-#include "MainThreadUtils.h"
-#include "nsUnicodeScriptCodes.h"
-#include "nsDataHashtable.h"
+#include "gfxTypes.h"
 #include "harfbuzz/hb.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
 #include "mozilla/FontPropertyTypes.h"
-#include "mozilla/gfx/2D.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/TypedEnumBits.h"
 #include "mozilla/UniquePtr.h"
-#include "mozilla/WeakPtr.h"
-#include "ThebesRLBoxTypes.h"
-#include <math.h>
+#include "nsDataHashtable.h"
+#include "nsDebug.h"
+#include "nsHashKeys.h"
+#include "nsISupports.h"
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+#include "nsUnicodeScriptCodes.h"
+#include "nscore.h"
 
-typedef struct gr_face gr_face;
-typedef struct FT_MM_Var_ FT_MM_Var;
-
-#ifdef DEBUG
-#  include <stdio.h>
-#endif
-
-struct gfxFontStyle;
+class FontInfoData;
 class gfxContext;
 class gfxFont;
 class gfxFontFamily;
-class gfxUserFontData;
+class gfxPlatformFontList;
 class gfxSVGGlyphs;
-class FontInfoData;
-struct FontListSizes;
+class gfxUserFontData;
 class nsAtom;
+struct FontListSizes;
+struct gfxFontFeature;
+struct gfxFontStyle;
+enum class eFontPresentation : uint8_t;
+
+namespace IPC {
+template <class P>
+struct ParamTraits;
+}
 
 namespace mozilla {
 class SVGContextPaint;
 namespace fontlist {
-struct Family;
 struct Face;
+struct Family;
 }  // namespace fontlist
+namespace gfx {
+struct DeviceColor;
+}
 }  // namespace mozilla
 
+typedef struct gr_face gr_face;
+typedef struct FT_MM_Var_ FT_MM_Var;
+
 #define NO_FONT_LANGUAGE_OVERRIDE 0
 
 class gfxCharacterMap : public gfxSparseBitSet {
diff --git a/gfx/thebes/gfxFontFamilyList.h b/gfx/thebes/gfxFontFamilyList.h
index 94f10a0b93d7..2eb926f97315 100644
--- a/gfx/thebes/gfxFontFamilyList.h
+++ b/gfx/thebes/gfxFontFamilyList.h
@@ -10,13 +10,12 @@
 #include "nsDebug.h"
 #include "nsISupportsImpl.h"
 #include "nsString.h"
-#include "nsStyleConsts.h"
 #include "nsUnicharUtils.h"
 #include "nsTArray.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/NotNull.h"
+#include "mozilla/ServoStyleConsts.h"
 #include "mozilla/StaticPtr.h"
-#include "mozilla/TimeStamp.h"
 
 namespace mozilla {
 
diff --git a/gfx/thebes/gfxFontInfoLoader.h b/gfx/thebes/gfxFontInfoLoader.h
index c300621acdc6..2f0b053a9031 100644
--- a/gfx/thebes/gfxFontInfoLoader.h
+++ b/gfx/thebes/gfxFontInfoLoader.h
@@ -10,12 +10,11 @@
 #include "nsIObserver.h"
 #include "nsITimer.h"
 #include "nsIThread.h"
-#include "nsRefPtrHashtable.h"
 #include "nsString.h"
-#include "gfxFont.h"
+#include "gfxFontEntry.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/TimeStamp.h"
-#include "nsISupportsImpl.h"
+#include "nsISupports.h"
 
 // data retrieved for a given face
 
diff --git a/gfx/thebes/gfxFontSrcPrincipal.h b/gfx/thebes/gfxFontSrcPrincipal.h
index bdf3ce612913..406d26915d4d 100644
--- a/gfx/thebes/gfxFontSrcPrincipal.h
+++ b/gfx/thebes/gfxFontSrcPrincipal.h
@@ -7,9 +7,10 @@
 #define MOZILLA_GFX_FONTSRCPRINCIPAL_H
 
 #include "nsCOMPtr.h"
-#include "nsIPrincipal.h"
 #include "PLDHashTable.h"
 
+class nsIPrincipal;
+
 namespace mozilla {
 namespace net {
 class nsSimpleURI;
diff --git a/gfx/thebes/gfxFontSrcURI.h b/gfx/thebes/gfxFontSrcURI.h
index 6a1206218dbc..26ea173b618a 100644
--- a/gfx/thebes/gfxFontSrcURI.h
+++ b/gfx/thebes/gfxFontSrcURI.h
@@ -7,9 +7,10 @@
 #define MOZILLA_GFX_FONTSRCURI_H
 
 #include "nsCOMPtr.h"
-#include "nsIURI.h"
 #include "PLDHashTable.h"
 
+class nsIURI;
+
 namespace mozilla {
 namespace net {
 class nsSimpleURI;
diff --git a/gfx/thebes/gfxFontUtils.h b/gfx/thebes/gfxFontUtils.h
index 83d32ffa83da..0c60ca3153bb 100644
--- a/gfx/thebes/gfxFontUtils.h
+++ b/gfx/thebes/gfxFontUtils.h
@@ -6,20 +6,35 @@
 #ifndef GFX_FONT_UTILS_H
 #define GFX_FONT_UTILS_H
 
-#include "gfxFontVariations.h"
+#include <string.h>
+#include <algorithm>
+#include <new>
+#include <utility>
 #include "gfxPlatform.h"
-#include "nsComponentManagerUtils.h"
-#include "nsTArray.h"
 #include "ipc/IPCMessageUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
 #include "mozilla/Casting.h"
-#include "mozilla/Encoding.h"
 #include "mozilla/EndianUtils.h"
-#include "mozilla/Likely.h"
+#include "mozilla/FontPropertyTypes.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/UniquePtr.h"
-
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+#include "nscore.h"
 #include "zlib.h"
-#include <algorithm>
+
+class PickleIterator;
+class gfxFontEntry;
+struct gfxFontVariationAxis;
+struct gfxFontVariationInstance;
+
+namespace mozilla {
+class Encoding;
+namespace gfx {
+struct DeviceColor;
+}
+}  // namespace mozilla
 
 /* Bug 341128 - w32api defines min/max which causes problems with <bitset> */
 #ifdef __MINGW32__
diff --git a/gfx/thebes/gfxPlatform.h b/gfx/thebes/gfxPlatform.h
index 3abf029880df..919992d852ed 100644
--- a/gfx/thebes/gfxPlatform.h
+++ b/gfx/thebes/gfxPlatform.h
@@ -7,7 +7,6 @@
 #define GFX_PLATFORM_H
 
 #include "mozilla/FontPropertyTypes.h"
-#include "mozilla/Logging.h"
 #include "mozilla/gfx/Types.h"
 #include "nsTArray.h"
 #include "nsString.h"
@@ -15,9 +14,7 @@
 #include "nsUnicodeScriptCodes.h"
 
 #include "gfxTypes.h"
-#include "gfxBlur.h"
 #include "gfxSkipChars.h"
-#include "nsRect.h"
 
 #include "qcms.h"
 
@@ -25,6 +22,7 @@
 #include "GfxInfoCollector.h"
 
 #include "mozilla/layers/CompositorTypes.h"
+#include "mozilla/layers/LayersTypes.h"
 #include "mozilla/layers/MemoryPressureObserver.h"
 
 class gfxASurface;
@@ -45,6 +43,7 @@ typedef struct FT_LibraryRec_* FT_Library;
 
 namespace mozilla {
 class FontFamilyList;
+class LogModule;
 namespace layers {
 class FrameStats;
 }
diff --git a/gfx/thebes/gfxUserFontSet.h b/gfx/thebes/gfxUserFontSet.h
index 8ce181f498e2..71ae925f1372 100644
--- a/gfx/thebes/gfxUserFontSet.h
+++ b/gfx/thebes/gfxUserFontSet.h
@@ -6,33 +6,53 @@
 #ifndef GFX_USER_FONT_SET_H
 #define GFX_USER_FONT_SET_H
 
+#include <new>
+#include "PLDHashTable.h"
 #include "gfxFontEntry.h"
-#include "gfxFontFamilyList.h"
-#include "gfxFontSrcPrincipal.h"
-#include "gfxFontSrcURI.h"
-#include "nsProxyRelease.h"
-#include "nsRefPtrHashtable.h"
-#include "nsCOMPtr.h"
-#include "nsIFontLoadCompleteCallback.h"
-#include "nsIMemoryReporter.h"
-#include "nsIRunnable.h"
-#include "nsIScriptError.h"
-#include "nsIReferrerInfo.h"
-#include "nsURIHashKey.h"
+#include "gfxFontUtils.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Attributes.h"
 #include "mozilla/FontPropertyTypes.h"
-#include "gfxFontConstants.h"
-#include "mozilla/LazyIdleThread.h"
-#include "mozilla/StaticPtr.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
+#include "nsCOMPtr.h"
+#include "nsHashKeys.h"
+#include "nsIMemoryReporter.h"
+#include "nsIObserver.h"
+#include "nsIScriptError.h"
+#include "nsISupports.h"
+#include "nsRefPtrHashtable.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "nscore.h"
+
+// Only needed for function bodies.
+#include <utility>                // for move, forward
+#include "MainThreadUtils.h"      // for NS_IsMainThread
+#include "gfxFontFeatures.h"      // for gfxFontFeature
+#include "gfxFontSrcPrincipal.h"  // for gfxFontSrcPrincipal
+#include "gfxFontSrcURI.h"        // for gfxFontSrcURI
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT_HELPER2, MOZ_ASSERT, MOZ_ASSERT_UNREACHABLE, MOZ_ASSER...
+#include "mozilla/HashFunctions.h"      // for HashBytes, HashGeneric
+#include "mozilla/TimeStamp.h"          // for TimeStamp
+#include "mozilla/gfx/FontVariation.h"  // for FontVariation
+#include "nsDebug.h"                    // for NS_WARNING
+#include "nsIReferrerInfo.h"            // for nsIReferrerInfo
 
 class gfxFont;
+class gfxUserFontSet;
+class nsIFontLoadCompleteCallback;
+class nsIRunnable;
+struct gfxFontStyle;
+struct gfxFontVariationAxis;
+struct gfxFontVariationInstance;
+template <class T>
+class nsMainThreadPtrHandle;
 
 namespace mozilla {
+class LogModule;
 class PostTraversalTask;
 enum class StyleFontDisplay : uint8_t;
-
-namespace gfx {
-struct FontVariation;
-}
 }  // namespace mozilla
 class nsFontFaceLoader;
 
diff --git a/image/imgIContainer.idl b/image/imgIContainer.idl
index 8e6c5f89498c..41cd795cebd9 100644
--- a/image/imgIContainer.idl
+++ b/image/imgIContainer.idl
@@ -10,10 +10,8 @@ webidl Document;
 
 %{C++
 #include "ImgDrawResult.h"
-#include "gfxContext.h"
-#include "gfxMatrix.h"
-#include "gfxRect.h"
-#include "mozilla/gfx/2D.h"
+#include "gfxPoint.h"
+#include "mozilla/gfx/Types.h"
 #include "mozilla/AspectRatio.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/RefPtr.h"
@@ -22,7 +20,15 @@ webidl Document;
 #include "nsTArray.h"
 #include "limits.h"
 
+class gfxContext;
+
 namespace mozilla {
+struct AspectRatio;
+
+namespace gfx {
+class SourceSurface;
+}
+
 namespace layers {
 class LayerManager;
 class ImageContainer;
diff --git a/intl/l10n/FluentBundle.h b/intl/l10n/FluentBundle.h
index b0f23163d06b..8a7e22706acf 100644
--- a/intl/l10n/FluentBundle.h
+++ b/intl/l10n/FluentBundle.h
@@ -8,7 +8,6 @@
 #define mozilla_intl_l10n_FluentBundle_h
 
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "mozilla/dom/FluentBinding.h"
@@ -19,6 +18,7 @@
 class nsIGlobalObject;
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 struct FluentMessage;
diff --git a/intl/l10n/FluentResource.h b/intl/l10n/FluentResource.h
index d51ce9f76c59..1d7f8b5e7eac 100644
--- a/intl/l10n/FluentResource.h
+++ b/intl/l10n/FluentResource.h
@@ -8,7 +8,6 @@
 #define mozilla_intl_l10n_FluentResource_h
 
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsWrapperCache.h"
 #include "mozilla/dom/FluentBinding.h"
diff --git a/intl/l10n/Localization.h b/intl/l10n/Localization.h
index d7e78e610d3b..3595721cb20d 100644
--- a/intl/l10n/Localization.h
+++ b/intl/l10n/Localization.h
@@ -10,7 +10,6 @@
 #include "nsWeakReference.h"
 #include "nsIObserver.h"
 #include "mozILocalization.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/Promise.h"
 #include "mozilla/dom/LocalizationBinding.h"
 #include "mozilla/dom/PromiseNativeHandler.h"
@@ -20,6 +19,8 @@ class nsIGlobalObject;
 using namespace mozilla::dom;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace intl {
 
 typedef Record<nsCString, Nullable<OwningUTF8StringOrDouble>> L10nArgs;
diff --git a/ipc/chromium/src/base/process_util.h b/ipc/chromium/src/base/process_util.h
index a6204d33475f..8876d79936f6 100644
--- a/ipc/chromium/src/base/process_util.h
+++ b/ipc/chromium/src/base/process_util.h
@@ -13,6 +13,7 @@
 #include "base/basictypes.h"
 
 #if defined(OS_WIN)
+#  include "mozilla/ipc/EnvironmentMap.h"
 #  include <windows.h>
 #  include <tlhelp32.h>
 #elif defined(OS_LINUX) || defined(__GLIBC__)
@@ -23,19 +24,18 @@
 #  include <mach/mach.h>
 #endif
 
-#include <functional>
+#include <cstddef>
 #include <map>
 #include <string>
+#include <utility>
 #include <vector>
 
-#include "base/command_line.h"
 #include "base/process.h"
 
 #include "mozilla/UniquePtr.h"
-#include "mozilla/ipc/EnvironmentMap.h"
 
 #if defined(MOZ_ENABLE_FORKSERVER)
-#  include "nsString.h"
+#  include "nsStringFwd.h"
 #  include "mozilla/Tuple.h"
 #  include "mozilla/ipc/FileDescriptorShuffle.h"
 
@@ -50,6 +50,8 @@ class FileDescriptor;
 struct kinfo_proc;
 #endif
 
+class CommandLine;
+
 namespace base {
 
 enum ProcessArchitecture {
diff --git a/ipc/chromium/src/base/process_util_linux.cc b/ipc/chromium/src/base/process_util_linux.cc
index 9cd7f26d9ff6..d3d946956242 100644
--- a/ipc/chromium/src/base/process_util_linux.cc
+++ b/ipc/chromium/src/base/process_util_linux.cc
@@ -31,6 +31,7 @@
 using namespace mozilla::ipc;
 #endif
 
+#include "base/command_line.h"
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "mozilla/ipc/FileDescriptor.h"
diff --git a/ipc/chromium/src/base/process_util_mac.mm b/ipc/chromium/src/base/process_util_mac.mm
index 30917ba02235..44db73c74024 100644
--- a/ipc/chromium/src/base/process_util_mac.mm
+++ b/ipc/chromium/src/base/process_util_mac.mm
@@ -12,6 +12,7 @@
 
 #include <string>
 
+#include "base/command_line.h"
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "mozilla/ipc/FileDescriptorShuffle.h"
diff --git a/ipc/chromium/src/base/process_util_posix.cc b/ipc/chromium/src/base/process_util_posix.cc
index 513396d87e56..929d0cba35d7 100644
--- a/ipc/chromium/src/base/process_util_posix.cc
+++ b/ipc/chromium/src/base/process_util_posix.cc
@@ -20,6 +20,7 @@
 #include <set>
 
 #include "base/basictypes.h"
+#include "base/command_line.h"
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "base/platform_thread.h"
diff --git a/ipc/chromium/src/base/process_util_win.cc b/ipc/chromium/src/base/process_util_win.cc
index e79f3054eb16..c37b6ebe2e0c 100644
--- a/ipc/chromium/src/base/process_util_win.cc
+++ b/ipc/chromium/src/base/process_util_win.cc
@@ -18,6 +18,7 @@
 #  define STDOUT_FILENO 1
 #endif
 
+#include "base/command_line.h"
 #include "base/histogram.h"
 #include "base/logging.h"
 #include "base/win_util.h"
diff --git a/ipc/chromium/src/chrome/common/ipc_channel.h b/ipc/chromium/src/chrome/common/ipc_channel.h
index 12a7bffb8640..92280bb0ebb0 100644
--- a/ipc/chromium/src/chrome/common/ipc_channel.h
+++ b/ipc/chromium/src/chrome/common/ipc_channel.h
@@ -7,10 +7,10 @@
 #ifndef CHROME_COMMON_IPC_CHANNEL_H_
 #define CHROME_COMMON_IPC_CHANNEL_H_
 
-#include <string>
-
+#include <cstdint>
 #include <queue>
-#include "chrome/common/ipc_message.h"
+#include "base/basictypes.h"
+#include "build/build_config.h"
 #include "mozilla/UniquePtr.h"
 
 #ifdef OS_WIN
@@ -19,6 +19,8 @@
 
 namespace IPC {
 
+class Message;
+
 //------------------------------------------------------------------------------
 
 class Channel {
diff --git a/ipc/chromium/src/chrome/common/ipc_message_utils.h b/ipc/chromium/src/chrome/common/ipc_message_utils.h
index 910f673282e6..d8bed78ac7b9 100644
--- a/ipc/chromium/src/chrome/common/ipc_message_utils.h
+++ b/ipc/chromium/src/chrome/common/ipc_message_utils.h
@@ -7,16 +7,19 @@
 #ifndef CHROME_COMMON_IPC_MESSAGE_UTILS_H_
 #define CHROME_COMMON_IPC_MESSAGE_UTILS_H_
 
+#include <cstdint>
+#include <map>
 #include <string>
 #include <type_traits>
-#include <vector>
-#include <map>
-
-#include "base/file_path.h"
-#include "base/process.h"
+#include <utility>
+#include "ErrorList.h"
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+#include "base/pickle.h"
 #include "base/string_util.h"
-#include "base/string16.h"
-#include "base/time.h"
+#include "build/build_config.h"
+#include "chrome/common/ipc_message.h"
 
 #if defined(OS_POSIX)
 #  include "chrome/common/file_descriptor_set_posix.h"
@@ -24,7 +27,6 @@
 #if defined(OS_WIN)
 #  include "windows.h"
 #endif
-#include "chrome/common/ipc_message.h"
 
 template <typename T>
 class RefPtr;
diff --git a/ipc/glue/BackgroundUtils.h b/ipc/glue/BackgroundUtils.h
index b2b0f66fe8cc..8a9c4e2aa0fa 100644
--- a/ipc/glue/BackgroundUtils.h
+++ b/ipc/glue/BackgroundUtils.h
@@ -9,7 +9,7 @@
 
 #include "ipc/IPCMessageUtils.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/BasePrincipal.h"
+#include "mozilla/OriginAttributes.h"
 #include "nsCOMPtr.h"
 #include "nscore.h"
 
@@ -48,6 +48,11 @@ struct ParamTraits<mozilla::OriginAttributes>
 }  // namespace IPC
 
 namespace mozilla {
+
+namespace dom {
+class Document;
+}
+
 namespace net {
 class ChildLoadInfoForwarderArgs;
 class LoadInfoArgs;
diff --git a/js/public/Value.h b/js/public/Value.h
index 3228c811c397..de73fb6fdd0c 100644
--- a/js/public/Value.h
+++ b/js/public/Value.h
@@ -11,8 +11,6 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/Casting.h"
-#include "mozilla/Compiler.h"
-#include "mozilla/EndianUtils.h"
 #include "mozilla/FloatingPoint.h"
 #include "mozilla/Likely.h"
 #include "mozilla/Maybe.h"
@@ -22,9 +20,8 @@
 #include "js-config.h"
 #include "jstypes.h"
 
-#include "js/GCAPI.h"
 #include "js/RootingAPI.h"
-#include "js/Utility.h"
+#include "js/TypeDecls.h"
 
 namespace JS {
 class JS_PUBLIC_API Value;
diff --git a/layout/base/GeometryUtils.h b/layout/base/GeometryUtils.h
index d6fe8d7f1227..eabbad530500 100644
--- a/layout/base/GeometryUtils.h
+++ b/layout/base/GeometryUtils.h
@@ -7,7 +7,6 @@
 #ifndef MOZILLA_GEOMETRYUTILS_H_
 #define MOZILLA_GEOMETRYUTILS_H_
 
-#include "mozilla/ErrorResult.h"
 #include "nsTArray.h"
 #include "nsCOMPtr.h"
 
@@ -19,6 +18,7 @@
 class nsINode;
 
 namespace mozilla {
+class ErrorResult;
 
 namespace dom {
 struct BoxQuadOptions;
diff --git a/layout/base/PresShell.h b/layout/base/PresShell.h
index dbaed664c605..787b2c5dc06d 100644
--- a/layout/base/PresShell.h
+++ b/layout/base/PresShell.h
@@ -13,7 +13,6 @@
 
 #include <stdio.h>  // for FILE definition
 #include "FrameMetrics.h"
-#include "GeckoProfiler.h"
 #include "TouchManager.h"
 #include "Units.h"
 #include "Visibility.h"
@@ -96,6 +95,10 @@ class GeckoMVMContext;
 class OverflowChangedTracker;
 class StyleSheet;
 
+#ifdef MOZ_GECKO_PROFILER
+class ProfileChunkedBuffer;
+#endif
+
 #ifdef ACCESSIBILITY
 namespace a11y {
 class DocAccessible;
diff --git a/layout/base/PresShellInlines.h b/layout/base/PresShellInlines.h
index cb79a245b2e2..6a6d858e38de 100644
--- a/layout/base/PresShellInlines.h
+++ b/layout/base/PresShellInlines.h
@@ -7,6 +7,7 @@
 #ifndef mozilla_PresShellInlines_h
 #define mozilla_PresShellInlines_h
 
+#include "GeckoProfiler.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/Element.h"
diff --git a/layout/base/SurfaceFromElementResult.h b/layout/base/SurfaceFromElementResult.h
index 4cf714c478d1..65c0e24f983f 100644
--- a/layout/base/SurfaceFromElementResult.h
+++ b/layout/base/SurfaceFromElementResult.h
@@ -7,6 +7,7 @@
 #ifndef mozilla_SurfaceFromElementResult_h
 #define mozilla_SurfaceFromElementResult_h
 
+#include "ImageContainer.h"
 #include "gfxTypes.h"
 #include "mozilla/gfx/Point.h"
 #include "nsCOMPtr.h"
@@ -27,10 +28,6 @@ namespace gfx {
 class SourceSurface;
 }
 
-namespace layers {
-class Image;
-}
-
 struct DirectDrawInfo {
   /* imgIContainer to directly draw to a context */
   nsCOMPtr<imgIContainer> mImgContainer;
diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h
index 5f5947ccd3f8..b55d4f1c2928 100644
--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -12,7 +12,6 @@
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/Maybe.h"
-#include "mozilla/ReflowOutput.h"
 #include "mozilla/RelativeTo.h"
 #include "mozilla/StaticPrefs_nglayout.h"
 #include "mozilla/SurfaceFromElementResult.h"
@@ -20,18 +19,15 @@
 #include "mozilla/ToString.h"
 #include "mozilla/TypedEnumBits.h"
 #include "mozilla/UniquePtr.h"
+#include "mozilla/WritingModes.h"
 #include "mozilla/layout/FrameChildList.h"
 #include "mozilla/layers/ScrollableLayerGuid.h"
 #include "mozilla/gfx/2D.h"
 
-#include "gfx2DGlue.h"
 #include "gfxPoint.h"
 #include "nsBoundingMetrics.h"
 #include "nsCSSPropertyIDSet.h"
-#include "nsClassHashtable.h"
-#include "nsGkAtoms.h"
 #include "nsThreadUtils.h"
-#include "ImageContainer.h"  // for layers::Image
 #include "Units.h"
 #include "mozilla/layers/LayersTypes.h"
 #include <limits>
@@ -80,6 +76,7 @@ class EventListenerManager;
 enum class LayoutFrameType : uint8_t;
 struct IntrinsicSize;
 struct ContainerLayerParameters;
+class ReflowOutput;
 class WritingMode;
 class DisplayItemClip;
 class EffectSet;
diff --git a/layout/base/nsPresContext.h b/layout/base/nsPresContext.h
index b0e98754e2ff..6f855fdd4935 100644
--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -18,7 +18,6 @@
 #include "mozilla/PreferenceSheet.h"
 #include "mozilla/PresShellForwards.h"
 #include "mozilla/ScrollStyles.h"
-#include "mozilla/ServoStyleSet.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/WeakPtr.h"
@@ -27,23 +26,20 @@
 #include "nsCompatibility.h"
 #include "nsCoord.h"
 #include "nsCOMPtr.h"
+#include "nsHashKeys.h"
 #include "nsRect.h"
 #include "nsStringFwd.h"
-#include "gfxFontConstants.h"
+#include "nsTHashtable.h"
 #include "nsAtom.h"
-#include "nsCRT.h"
 #include "nsIWidgetListener.h"  // for nsSizeMode
 #include "nsGkAtoms.h"
 #include "nsCycleCollectionParticipant.h"
 #include "nsChangeHint.h"
-#include <algorithm>
 #include "gfxTypes.h"
 #include "gfxRect.h"
 #include "nsTArray.h"
-#include "prclist.h"
 #include "nsThreadUtils.h"
 #include "Units.h"
-#include "prenv.h"
 
 class nsBidi;
 class nsIPrintSettings;
@@ -81,6 +77,7 @@ class EventStateManager;
 class CounterStyleManager;
 class PresShell;
 class RestyleManager;
+class ServoStyleSet;
 class StaticPresData;
 struct MediaFeatureChange;
 enum class MediaFeatureChangePropagation : uint8_t;
diff --git a/layout/generic/nsIAnonymousContentCreator.h b/layout/generic/nsIAnonymousContentCreator.h
index 789759202890..2d27e4455f58 100644
--- a/layout/generic/nsIAnonymousContentCreator.h
+++ b/layout/generic/nsIAnonymousContentCreator.h
@@ -13,13 +13,11 @@
 #define nsIAnonymousContentCreator_h___
 
 #include "mozilla/AnonymousContentKey.h"
-#include "mozilla/ComputedStyle.h"
 
 #include "nsQueryFrame.h"
 #include "nsTArrayForwardDeclare.h"
 
 class nsIContent;
-class nsIFrame;
 
 /**
  * Any source for anonymous content can implement this interface to provide it.
diff --git a/layout/style/ComputedStyleInlines.h b/layout/style/ComputedStyleInlines.h
index 56a3054ec0c5..81646c95d116 100644
--- a/layout/style/ComputedStyleInlines.h
+++ b/layout/style/ComputedStyleInlines.h
@@ -15,9 +15,11 @@
 #define ComputedStyleInlines_h
 
 #include "mozilla/ComputedStyle.h"
-#include "mozilla/ServoComputedDataInlines.h"
-#include "mozilla/ServoUtils.h"
-#include "nsPresContext.h"
+
+#include "MainThreadUtils.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Unused.h"
+#include "nsStyleStruct.h"
 
 namespace mozilla {
 
diff --git a/layout/style/GroupRule.h b/layout/style/GroupRule.h
index df357f446654..258e23def11a 100644
--- a/layout/style/GroupRule.h
+++ b/layout/style/GroupRule.h
@@ -13,7 +13,6 @@
 #define mozilla_css_GroupRule_h__
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/ServoCSSRuleList.h"
 #include "mozilla/css/Rule.h"
@@ -21,6 +20,7 @@
 
 namespace mozilla {
 
+class ErrorResult;
 class StyleSheet;
 
 namespace dom {
diff --git a/layout/style/MediaList.h b/layout/style/MediaList.h
index 338c0f3cdc88..fd8ca84fc17c 100644
--- a/layout/style/MediaList.h
+++ b/layout/style/MediaList.h
@@ -10,7 +10,6 @@
 #define mozilla_dom_MediaList_h
 
 #include "mozilla/dom/BindingDeclarations.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/ServoBindingTypes.h"
 #include "mozilla/ServoUtils.h"
 
@@ -19,6 +18,7 @@
 class nsMediaQueryResultCacheKey;
 
 namespace mozilla {
+class ErrorResult;
 class StyleSheet;
 
 namespace dom {
diff --git a/layout/style/StyleSheet.h b/layout/style/StyleSheet.h
index 1696e25dde17..0eb0eb7ac423 100644
--- a/layout/style/StyleSheet.h
+++ b/layout/style/StyleSheet.h
@@ -14,17 +14,17 @@
 #include "mozilla/MozPromise.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/ServoBindingTypes.h"
-#include "mozilla/ServoUtils.h"
+#include "mozilla/ServoTypes.h"
 #include "mozilla/StyleSheetInfo.h"
-#include "mozilla/URLExtraData.h"
 #include "nsICSSLoaderObserver.h"
+#include "nsIPrincipal.h"
 #include "nsWrapperCache.h"
-#include "nsCompatibility.h"
 #include "nsStringFwd.h"
 
+class nsIGlobalObject;
 class nsINode;
 class nsIPrincipal;
-struct RawServoSharedMemoryBuilder;
+struct ServoCssRules;
 class nsIReferrerInfo;
 
 namespace mozilla {
@@ -53,7 +53,6 @@ class CSSRuleList;
 class DocumentOrShadowRoot;
 class MediaList;
 class ShadowRoot;
-class SRIMetadata;
 struct CSSStyleSheetInit;
 }  // namespace dom
 
diff --git a/layout/style/StyleSheetInfo.h b/layout/style/StyleSheetInfo.h
index 1fb111b955dd..158a731ddaa7 100644
--- a/layout/style/StyleSheetInfo.h
+++ b/layout/style/StyleSheetInfo.h
@@ -11,10 +11,11 @@
 #include "mozilla/dom/SRIMetadata.h"
 #include "mozilla/CORSMode.h"
 
-#include "nsIURI.h"
 #include "nsIReferrerInfo.h"
 
 class nsIPrincipal;
+class nsIURI;
+struct RawServoStyleSheetContents;
 
 namespace mozilla {
 class StyleSheet;
diff --git a/layout/style/URLExtraData.h b/layout/style/URLExtraData.h
index e2eebad91c0c..71c002de90a8 100644
--- a/layout/style/URLExtraData.h
+++ b/layout/style/URLExtraData.h
@@ -11,7 +11,6 @@
 
 #include <utility>
 
-#include "ReferrerInfo.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/UserAgentStyleSheetID.h"
 #include "mozilla/dom/URL.h"
diff --git a/layout/style/nsICSSDeclaration.h b/layout/style/nsICSSDeclaration.h
index e249f6637589..8ec2d275d59e 100644
--- a/layout/style/nsICSSDeclaration.h
+++ b/layout/style/nsICSSDeclaration.h
@@ -24,12 +24,13 @@
 #include "mozilla/ErrorResult.h"
 #include "nsWrapperCache.h"
 #include "nsStringFwd.h"
-#include "mozilla/ErrorResult.h"
 #include "nsCOMPtr.h"
 
 class nsINode;
 class nsIPrincipal;
 namespace mozilla {
+class ErrorResult;
+
 namespace css {
 class Rule;
 }  // namespace css
diff --git a/layout/style/nsStyleStruct.h b/layout/style/nsStyleStruct.h
index cf934e291f66..2a748455078a 100644
--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -16,8 +16,6 @@
 #include "mozilla/Maybe.h"
 #include "mozilla/ServoStyleConstsInlines.h"
 #include "mozilla/StaticPrefs_layout.h"
-#include "mozilla/StaticPtr.h"
-#include "mozilla/StyleColorInlines.h"
 #include "mozilla/UniquePtr.h"
 #include "nsColor.h"
 #include "nsCoord.h"
@@ -27,28 +25,21 @@
 #include "nsStyleConsts.h"
 #include "nsChangeHint.h"
 #include "nsTimingFunction.h"
-#include "nsCOMPtr.h"
 #include "nsTArray.h"
-#include "nsCSSValue.h"
 #include "imgIContainer.h"
 #include "imgRequestProxy.h"
-#include "Orientation.h"
 #include "CounterStyleManager.h"
 #include <cstddef>  // offsetof()
-#include <utility>
 #include "X11UndefineNone.h"
 
 class nsIFrame;
 class nsIURI;
 class nsTextFrame;
-class nsPresContext;
 struct nsStyleDisplay;
 struct nsStyleVisibility;
 namespace mozilla {
 class ComputedStyle;
-namespace dom {
-class ImageTracker;
-}  // namespace dom
+
 }  // namespace mozilla
 
 namespace mozilla {
diff --git a/mfbt/ArrayUtils.h b/mfbt/ArrayUtils.h
index 89fcfdc820a7..0d55bb1f6546 100644
--- a/mfbt/ArrayUtils.h
+++ b/mfbt/ArrayUtils.h
@@ -14,18 +14,22 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 
-#include <algorithm>
 #include <stddef.h>
+#include <stdint.h>
 
 #ifdef __cplusplus
+#  include <algorithm>
 #  include <type_traits>
 
 #  include "mozilla/Alignment.h"
-#  include "mozilla/Array.h"
-#  include "mozilla/EnumeratedArray.h"
 
 namespace mozilla {
 
+template <typename T, size_t Length>
+class Array;
+template <typename IndexType, IndexType SizeAsEnumValue, typename ValueType>
+class EnumeratedArray;
+
 /*
  * Safely subtract two pointers when it is known that aEnd >= aBegin, yielding a
  * size_t result.
diff --git a/mfbt/Buffer.h b/mfbt/Buffer.h
index 4d90ee874135..c4e0a4be92e0 100644
--- a/mfbt/Buffer.h
+++ b/mfbt/Buffer.h
@@ -5,9 +5,10 @@
 #ifndef mozilla_Buffer_h
 #define mozilla_Buffer_h
 
-#include <algorithm>
+#include <cstddef>
 #include <iterator>
 
+#include "mozilla/Assertions.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/Span.h"
 #include "mozilla/UniquePtr.h"
diff --git a/mfbt/BufferList.h b/mfbt/BufferList.h
index 7bcba36b61b7..b59a4c27cabb 100644
--- a/mfbt/BufferList.h
+++ b/mfbt/BufferList.h
@@ -7,17 +7,14 @@
 #ifndef mozilla_BufferList_h
 #define mozilla_BufferList_h
 
-#include <string.h>
-
 #include <algorithm>
-#include <type_traits>
-#include <utility>
+#include <cstdint>
+#include <cstring>
 
-#include "mozilla/AllocPolicy.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/MemoryReporting.h"
-#include "mozilla/ScopeExit.h"
-#include "mozilla/Types.h"
 #include "mozilla/Vector.h"
 
 // BufferList represents a sequence of buffers of data. A BufferList can choose
diff --git a/mfbt/DoublyLinkedList.h b/mfbt/DoublyLinkedList.h
index 0b93f85ff228..f9c374550622 100644
--- a/mfbt/DoublyLinkedList.h
+++ b/mfbt/DoublyLinkedList.h
@@ -10,7 +10,9 @@
 #define mozilla_DoublyLinkedList_h
 
 #include <algorithm>
+#include <iosfwd>
 #include <iterator>
+#include <type_traits>
 
 #include "mozilla/Assertions.h"
 
diff --git a/mfbt/FloatingPoint.h b/mfbt/FloatingPoint.h
index 28d41ef19984..a2625a4e2232 100644
--- a/mfbt/FloatingPoint.h
+++ b/mfbt/FloatingPoint.h
@@ -20,7 +20,6 @@
 #include <climits>
 #include <limits>
 #include <stdint.h>
-#include <type_traits>
 
 namespace mozilla {
 
diff --git a/mfbt/LinkedList.h b/mfbt/LinkedList.h
index 5ca0c5d33d4e..a05e21cd2f9c 100644
--- a/mfbt/LinkedList.h
+++ b/mfbt/LinkedList.h
@@ -64,6 +64,7 @@
 #ifndef mozilla_LinkedList_h
 #define mozilla_LinkedList_h
 
+#include <algorithm>
 #include <utility>
 
 #include "mozilla/Assertions.h"
diff --git a/mfbt/PodOperations.h b/mfbt/PodOperations.h
index c76e1b2557c0..f4e5da4c799c 100644
--- a/mfbt/PodOperations.h
+++ b/mfbt/PodOperations.h
@@ -15,16 +15,17 @@
 #ifndef mozilla_PodOperations_h
 #define mozilla_PodOperations_h
 
-#include "mozilla/Array.h"
-#include "mozilla/ArrayUtils.h"
+#include "mozilla/Assertions.h"
 #include "mozilla/Attributes.h"
 
-#include <algorithm>
 #include <stdint.h>
 #include <string.h>
 
 namespace mozilla {
 
+template <typename T, size_t Length>
+class Array;
+
 template <typename T>
 class NotNull;
 
diff --git a/mfbt/SPSCQueue.h b/mfbt/SPSCQueue.h
index 4d872251086c..0e116c546831 100644
--- a/mfbt/SPSCQueue.h
+++ b/mfbt/SPSCQueue.h
@@ -14,9 +14,11 @@
 #include "mozilla/PodOperations.h"
 #include <algorithm>
 #include <atomic>
-#include <cstdint>
+#include <cstddef>
+#include <limits>
 #include <memory>
 #include <thread>
+#include <type_traits>
 
 namespace mozilla {
 
diff --git a/mfbt/SmallPointerArray.h b/mfbt/SmallPointerArray.h
index 7863f6e04e52..c63e3980f9a5 100644
--- a/mfbt/SmallPointerArray.h
+++ b/mfbt/SmallPointerArray.h
@@ -13,7 +13,7 @@
 #include "mozilla/PodOperations.h"
 
 #include <algorithm>
-#include <iterator>
+#include <cstddef>
 #include <new>
 #include <vector>
 
diff --git a/mfbt/Span.h b/mfbt/Span.h
index dc14de213728..6f1d1d437200 100644
--- a/mfbt/Span.h
+++ b/mfbt/Span.h
@@ -22,22 +22,25 @@
 #ifndef mozilla_Span_h
 #define mozilla_Span_h
 
-#include <algorithm>
 #include <array>
+#include <cstddef>
+#include <cstdint>
 #include <iterator>
 #include <limits>
 #include <string>
 #include <type_traits>
 #include <utility>
 
-#include "mozilla/Array.h"
 #include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
 #include "mozilla/Casting.h"
-#include "mozilla/IntegerTypeTraits.h"
 #include "mozilla/UniquePtr.h"
 
 namespace mozilla {
 
+template <typename T, size_t Length>
+class Array;
+
 // Stuff from gsl_util
 
 // narrow_cast(): a searchable way to do narrowing casts of values
diff --git a/modules/libpref/Preferences.h b/modules/libpref/Preferences.h
index 4b5f2c1f2284..137f0fdb75de 100644
--- a/modules/libpref/Preferences.h
+++ b/modules/libpref/Preferences.h
@@ -15,7 +15,6 @@
 
 #include "mozilla/Atomics.h"
 #include "mozilla/MemoryReporting.h"
-#include "mozilla/Result.h"
 #include "mozilla/StaticPtr.h"
 #include "nsCOMPtr.h"
 #include "nsIObserver.h"
diff --git a/netwerk/base/nsILoadInfo.idl b/netwerk/base/nsILoadInfo.idl
index 34946f980b88..be5af09a5df1 100644
--- a/netwerk/base/nsILoadInfo.idl
+++ b/netwerk/base/nsILoadInfo.idl
@@ -21,8 +21,8 @@ webidl BrowsingContext;
 native LoadContextRef(already_AddRefed<nsISupports>);
 %{C++
 #include "nsTArray.h"
-#include "mozilla/BasePrincipal.h"
 #include "mozilla/LoadTainting.h"
+#include "mozilla/OriginAttributes.h"
 #include "mozilla/UniquePtr.h"
 #include "nsStringFwd.h"
 
diff --git a/netwerk/base/nsNetworkInfoService.h b/netwerk/base/nsNetworkInfoService.h
index 7f40b840e623..d7b449b96fcd 100644
--- a/netwerk/base/nsNetworkInfoService.h
+++ b/netwerk/base/nsNetworkInfoService.h
@@ -8,7 +8,6 @@
 #define mozilla_net_nsNetworkInfoService_h
 
 #include "nsISupportsImpl.h"
-#include "mozilla/ErrorResult.h"
 
 #include "nsINetworkInfoService.h"
 
diff --git a/netwerk/ipc/DocumentChannel.cpp b/netwerk/ipc/DocumentChannel.cpp
index e62ce6780b47..426ef9267bd0 100644
--- a/netwerk/ipc/DocumentChannel.cpp
+++ b/netwerk/ipc/DocumentChannel.cpp
@@ -5,34 +5,41 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "DocumentChannel.h"
+#include "mozilla/net/DocumentChannel.h"
 
-#include "SerializedLoadContext.h"
-#include "mozIThirdPartyUtil.h"
+#include <inttypes.h>
+#include <utility>
+#include "mozIDOMWindow.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Assertions.h"
 #include "mozilla/LoadInfo.h"
-#include "mozilla/StaticPrefs_browser.h"
-#include "mozilla/dom/BrowserChild.h"
-#include "mozilla/dom/ContentChild.h"
-#include "mozilla/dom/nsCSPContext.h"
-#include "mozilla/extensions/StreamFilterParent.h"
-#include "mozilla/ipc/IPCStreamUtils.h"
-#include "mozilla/ipc/URIUtils.h"
+#include "mozilla/Logging.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/Document.h"
 #include "mozilla/net/DocumentChannelChild.h"
-#include "mozilla/net/HttpChannelChild.h"
-#include "mozilla/net/NeckoChild.h"
 #include "mozilla/net/ParentProcessDocumentChannel.h"
-#include "mozilla/net/UrlClassifierCommon.h"
-#include "nsContentSecurityManager.h"
+#include "nsCOMPtr.h"
+#include "nsDebug.h"
 #include "nsDocShell.h"
 #include "nsDocShellLoadState.h"
 #include "nsHttpHandler.h"
-#include "nsIInputStreamChannel.h"
+#include "nsIContentPolicy.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsILoadContext.h"
+#include "nsILoadGroup.h"
+#include "nsILoadInfo.h"
+#include "nsIStreamListener.h"
+#include "nsIURI.h"
 #include "nsMimeTypes.h"
 #include "nsNetUtil.h"
-#include "nsQueryObject.h"
-#include "nsSerializationHelper.h"
-#include "nsStringStream.h"
-#include "nsURLHelper.h"
+#include "nsPIDOMWindow.h"
+#include "nsPIDOMWindowInlines.h"
+#include "nsStringFwd.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+#include "nscore.h"
 
 using namespace mozilla::dom;
 using namespace mozilla::ipc;
diff --git a/netwerk/protocol/http/HttpBaseChannel.h b/netwerk/protocol/http/HttpBaseChannel.h
index d327316b02ed..a26ad5a9e530 100644
--- a/netwerk/protocol/http/HttpBaseChannel.h
+++ b/netwerk/protocol/http/HttpBaseChannel.h
@@ -11,23 +11,15 @@
 #include <utility>
 
 #include "mozilla/Atomics.h"
-#include "mozilla/IntegerPrintfMacros.h"
-#include "mozilla/Tuple.h"
 #include "mozilla/dom/DOMTypes.h"
-#include "mozilla/dom/ReferrerInfo.h"
-#include "mozilla/net/ChannelEventQueue.h"
 #include "mozilla/net/DNS.h"
 #include "mozilla/net/NeckoCommon.h"
 #include "mozilla/net/PrivateBrowsingChannel.h"
-#include "nsCOMArray.h"
 #include "nsCOMPtr.h"
 #include "nsHashPropertyBag.h"
 #include "nsHttp.h"
-#include "nsHttpConnectionInfo.h"
 #include "nsHttpHandler.h"
 #include "nsHttpRequestHead.h"
-#include "nsHttpResponseHead.h"
-#include "nsIApplicationCache.h"
 #include "nsIClassOfService.h"
 #include "nsIClassifiedChannel.h"
 #include "nsIConsoleReportCollector.h"
@@ -37,9 +29,7 @@
 #include "nsIHttpChannel.h"
 #include "nsIHttpChannelInternal.h"
 #include "nsILoadInfo.h"
-#include "nsIProgressEventSink.h"
 #include "nsIResumableChannel.h"
-#include "nsISecurityConsoleMessage.h"
 #include "nsIStringEnumerator.h"
 #include "nsISupportsPriority.h"
 #include "nsIThrottledInputChannel.h"
@@ -47,7 +37,6 @@
 #include "nsITraceableChannel.h"
 #include "nsIURI.h"
 #include "nsIUploadChannel2.h"
-#include "nsProxyInfo.h"
 #include "nsStringEnumerator.h"
 #include "nsTArray.h"
 #include "nsThreadUtils.h"
@@ -59,6 +48,7 @@
     }                                                \
   }
 
+class nsIProgressEventSink;
 class nsISecurityConsoleMessage;
 class nsIPrincipal;
 
diff --git a/storage/mozStorageAsyncStatementParams.h b/storage/mozStorageAsyncStatementParams.h
index 3d0697531a4f..4c6f97052c87 100644
--- a/storage/mozStorageAsyncStatementParams.h
+++ b/storage/mozStorageAsyncStatementParams.h
@@ -8,11 +8,12 @@
 #define mozilla_storage_mozStorageAsyncStatementParams_h_
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsPIDOMWindow.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace storage {
 
 class AsyncStatement;
diff --git a/storage/mozStorageStatementParams.h b/storage/mozStorageStatementParams.h
index ea2b078d0010..647e111b42ec 100644
--- a/storage/mozStorageStatementParams.h
+++ b/storage/mozStorageStatementParams.h
@@ -8,11 +8,12 @@
 #define MOZSTORAGESTATEMENTPARAMS_H
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsPIDOMWindow.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace storage {
 
 class Statement;
diff --git a/storage/mozStorageStatementRow.h b/storage/mozStorageStatementRow.h
index 5c783b4ad82b..02c43749c630 100644
--- a/storage/mozStorageStatementRow.h
+++ b/storage/mozStorageStatementRow.h
@@ -8,11 +8,12 @@
 #define MOZSTORAGESTATEMENTROW_H
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "nsPIDOMWindow.h"
 #include "nsWrapperCache.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace storage {
 
 class Statement;
diff --git a/toolkit/components/antitracking/ContentBlockingLog.cpp b/toolkit/components/antitracking/ContentBlockingLog.cpp
index d8cd4e508a26..42d5a9ccd71e 100644
--- a/toolkit/components/antitracking/ContentBlockingLog.cpp
+++ b/toolkit/components/antitracking/ContentBlockingLog.cpp
@@ -8,19 +8,17 @@
 #include "ContentBlockingLog.h"
 
 #include "nsITrackingDBService.h"
-#include "nsStringStream.h"
+#include "nsServiceManagerUtils.h"
 #include "nsTArray.h"
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/HashFunctions.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/RandomNum.h"
+#include "mozilla/ReverseIterator.h"
 #include "mozilla/StaticPrefs_browser.h"
 #include "mozilla/StaticPrefs_privacy.h"
 #include "mozilla/StaticPrefs_telemetry.h"
 #include "mozilla/Telemetry.h"
-#include "mozilla/Unused.h"
 #include "mozilla/XorShift128PlusRNG.h"
-#include "mozilla/ipc/IPCStreamUtils.h"
 
 namespace mozilla {
 
diff --git a/toolkit/components/extensions/webrequest/StreamFilterChild.h b/toolkit/components/extensions/webrequest/StreamFilterChild.h
index 641f4250516c..9cc6e04cce30 100644
--- a/toolkit/components/extensions/webrequest/StreamFilterChild.h
+++ b/toolkit/components/extensions/webrequest/StreamFilterChild.h
@@ -11,12 +11,13 @@
 #include "mozilla/extensions/PStreamFilterChild.h"
 #include "mozilla/extensions/StreamFilter.h"
 
-#include "mozilla/ErrorResult.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/dom/StreamFilterBinding.h"
 #include "nsISupportsImpl.h"
 
 namespace mozilla {
+class ErrorResult;
+
 namespace extensions {
 
 using mozilla::dom::StreamFilterStatus;
diff --git a/toolkit/components/perfmonitoring/PerformanceUtils.cpp b/toolkit/components/perfmonitoring/PerformanceUtils.cpp
index 9abcc60d0969..5822c4d225ca 100644
--- a/toolkit/components/perfmonitoring/PerformanceUtils.cpp
+++ b/toolkit/components/perfmonitoring/PerformanceUtils.cpp
@@ -4,22 +4,18 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "nsThreadUtils.h"
 #include "mozilla/PerformanceUtils.h"
-#include "mozilla/ResultExtensions.h"
+
+#include "mozilla/dom/DOMTypes.h"
 #include "mozilla/dom/DocGroup.h"
-#include "mozilla/dom/BrowserChild.h"
 #include "mozilla/dom/BrowsingContextGroup.h"
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/WorkerDebugger.h"
 #include "mozilla/dom/WorkerDebuggerManager.h"
 
 #include "MediaDecoder.h"
-#include "XPCJSMemoryReporter.h"
 #include "jsfriendapi.h"
-#include "js/MemoryMetrics.h"
-#include "nsWindowMemoryReporter.h"
+#include "nsGlobalWindowOuter.h"
 #include "nsWindowSizes.h"
 
 using namespace mozilla;
diff --git a/toolkit/components/sessionstore/SessionStoreUtils.h b/toolkit/components/sessionstore/SessionStoreUtils.h
index 054bcb6b6f5d..b52ab4f48335 100644
--- a/toolkit/components/sessionstore/SessionStoreUtils.h
+++ b/toolkit/components/sessionstore/SessionStoreUtils.h
@@ -8,7 +8,6 @@
 #define mozilla_dom_SessionStoreUtils_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/ErrorResult.h"
 #include "mozilla/dom/BindingDeclarations.h"
 #include "mozilla/dom/SessionStoreUtilsBinding.h"
 #include "SessionStoreData.h"
@@ -17,6 +16,8 @@ class nsIDocument;
 class nsGlobalWindowInner;
 
 namespace mozilla {
+class ErrorResult;
+
 namespace dom {
 
 class GlobalObject;
diff --git a/toolkit/components/telemetry/core/ipc/TelemetryComms.h b/toolkit/components/telemetry/core/ipc/TelemetryComms.h
index 367214b0ac25..83d3216bc775 100644
--- a/toolkit/components/telemetry/core/ipc/TelemetryComms.h
+++ b/toolkit/components/telemetry/core/ipc/TelemetryComms.h
@@ -9,8 +9,8 @@
 #include "ipc/IPCMessageUtils.h"
 #include "mozilla/TelemetryProcessEnums.h"
 #include "mozilla/TimeStamp.h"
+#include "mozilla/Variant.h"
 #include "nsITelemetry.h"
-#include "nsVariant.h"
 
 namespace mozilla {
 namespace Telemetry {
diff --git a/toolkit/xre/nsEmbedFunctions.cpp b/toolkit/xre/nsEmbedFunctions.cpp
index c9ce8bcdb97f..b689b1fa2c66 100644
--- a/toolkit/xre/nsEmbedFunctions.cpp
+++ b/toolkit/xre/nsEmbedFunctions.cpp
@@ -4,8 +4,6 @@
 
 #include "mozilla/DebugOnly.h"
 
-#include "base/basictypes.h"
-
 #include "nsXULAppAPI.h"
 
 #include <stdlib.h>
@@ -17,7 +15,6 @@
 
 #include "nsIAppShell.h"
 #include "nsAppStartupNotifier.h"
-#include "nsIFile.h"
 #include "nsIToolkitProfile.h"
 
 #ifdef XP_WIN
@@ -27,10 +24,7 @@
 #  include "mozilla/WinDllServices.h"
 #endif
 
-#include "nsAppDirectoryServiceDefs.h"
 #include "nsAppRunner.h"
-#include "nsAutoRef.h"
-#include "nsDirectoryServiceDefs.h"
 #include "nsExceptionHandler.h"
 #include "nsString.h"
 #include "nsThreadUtils.h"
@@ -39,6 +33,7 @@
 #include "nsXREDirProvider.h"
 #ifdef MOZ_ASAN_REPORTER
 #  include "CmdLineAndEnvUtils.h"
+#  include "nsIFile.h"
 #endif
 
 #include "mozilla/Omnijar.h"
@@ -46,13 +41,10 @@
 #  include "nsVersionComparator.h"
 #  include "chrome/common/mach_ipc_mac.h"
 #endif
-#include "nsX11ErrorHandler.h"
 #include "nsGDKErrorHandler.h"
 #include "base/at_exit.h"
-#include "base/command_line.h"
 #include "base/message_loop.h"
 #include "base/process_util.h"
-#include "chrome/common/child_process.h"
 #if defined(MOZ_WIDGET_ANDROID)
 #  include "chrome/common/ipc_channel.h"
 #  include "mozilla/jni/Utils.h"
@@ -66,18 +58,14 @@
 #include "mozilla/UniquePtr.h"
 
 #include "mozilla/ipc/BrowserProcessSubThread.h"
-#include "mozilla/ipc/GeckoChildProcessHost.h"
 #include "mozilla/ipc/IOThreadChild.h"
 #include "mozilla/ipc/ProcessChild.h"
-#include "ScopedXREEmbed.h"
 
 #include "mozilla/plugins/PluginProcessChild.h"
 #include "mozilla/dom/ContentProcess.h"
 #include "mozilla/dom/ContentParent.h"
-#include "mozilla/dom/ContentChild.h"
 
 #include "mozilla/ipc/TestShellParent.h"
-#include "mozilla/ipc/XPCShellEnvironment.h"
 #if defined(XP_WIN)
 #  include "mozilla/WindowsConsole.h"
 #  include "mozilla/WindowsDllBlocklist.h"
@@ -99,7 +87,6 @@
 #if defined(MOZ_SANDBOX)
 #  include "XREChildData.h"
 #  include "mozilla/SandboxSettings.h"
-#  include "mozilla/Preferences.h"
 #endif
 
 #if defined(XP_LINUX) && defined(MOZ_SANDBOX)
diff --git a/tools/profiler/core/ProfiledThreadData.cpp b/tools/profiler/core/ProfiledThreadData.cpp
index 6626b6b377df..a6c2527cb7cc 100644
--- a/tools/profiler/core/ProfiledThreadData.cpp
+++ b/tools/profiler/core/ProfiledThreadData.cpp
@@ -9,8 +9,9 @@
 #include "ProfileBuffer.h"
 
 #include "js/TraceLoggerAPI.h"
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/ProfileJSONWriter.h"
+#include "mozilla/Span.h"
+#include "nsXULAppAPI.h"
 
 #if defined(GP_OS_darwin)
 #  include <pthread.h>
@@ -216,9 +217,9 @@ int StreamSamplesAndMarkers(const char* aName, int aThreadId,
   int processedThreadId = 0;
 
   aWriter.StringProperty("processType",
-                         MakeStringSpan(XRE_GetProcessTypeString()));
+                         mozilla::MakeStringSpan(XRE_GetProcessTypeString()));
 
-  aWriter.StringProperty("name", MakeStringSpan(aName));
+  aWriter.StringProperty("name", mozilla::MakeStringSpan(aName));
 
   // Use given process name (if any), unless we're the parent process.
   if (XRE_IsParentProcess()) {
diff --git a/uriloader/preload/PreloaderBase.h b/uriloader/preload/PreloaderBase.h
index acbc41cb97ba..dcd37382178f 100644
--- a/uriloader/preload/PreloaderBase.h
+++ b/uriloader/preload/PreloaderBase.h
@@ -8,14 +8,12 @@
 #include "mozilla/Maybe.h"
 #include "mozilla/PreloadHashKey.h"
 #include "mozilla/WeakPtr.h"
-#include "nsIChannelEventSink.h"
-#include "nsIInterfaceRequestor.h"
-#include "nsIRedirectResultListener.h"
+#include "nsCOMPtr.h"
+#include "nsISupports.h"
 #include "nsITimer.h"
 #include "nsIURI.h"
+#include "nsIWeakReferenceUtils.h"
 #include "nsTArray.h"
-#include "nsProxyRelease.h"
-#include "nsWeakReference.h"
 
 class nsIChannel;
 class nsINode;
diff --git a/widget/CompositorWidget.h b/widget/CompositorWidget.h
index 34237a288b13..6417926a8377 100644
--- a/widget/CompositorWidget.h
+++ b/widget/CompositorWidget.h
@@ -8,10 +8,13 @@
 #include "nsISupports.h"
 #include "mozilla/RefPtr.h"
 #include "Units.h"
-#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Rect.h"
 #include "mozilla/layers/CompositorOptions.h"
 #include "mozilla/layers/LayersTypes.h"
-#include "mozilla/layers/NativeLayer.h"
+
+#ifdef MOZ_IS_GCC
+#  include "mozilla/layers/NativeLayer.h"
+#endif
 
 class nsIWidget;
 class nsBaseWidget;
@@ -25,7 +28,7 @@ namespace layers {
 class Compositor;
 class LayerManager;
 class LayerManagerComposite;
-class Compositor;
+class NativeLayerRoot;
 }  // namespace layers
 namespace gfx {
 class DrawTarget;
diff --git a/widget/ContentCache.h b/widget/ContentCache.h
index 8c202fd27537..8fcc6fec96f1 100644
--- a/widget/ContentCache.h
+++ b/widget/ContentCache.h
@@ -10,15 +10,17 @@
 
 #include <stdint.h>
 
+#include "mozilla/widget/IMEData.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/CheckedInt.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/WritingModes.h"
-#include "nsIWidget.h"
 #include "nsString.h"
 #include "nsTArray.h"
 #include "Units.h"
 
+class nsIWidget;
+
 namespace mozilla {
 
 class ContentCacheInParent;
diff --git a/widget/WidgetUtils.h b/widget/WidgetUtils.h
index a93fe27f06bb..0a0435ddd6f5 100644
--- a/widget/WidgetUtils.h
+++ b/widget/WidgetUtils.h
@@ -8,12 +8,11 @@
 #ifndef mozilla_WidgetUtils_h
 #define mozilla_WidgetUtils_h
 
-#include "mozilla/EventForwards.h"
+#include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/gfx/Matrix.h"
-#include "nsCOMPtr.h"
-#include "nsIWidget.h"
 #include "nsRect.h"
 
+class nsIWidget;
 class nsPIDOMWindowOuter;
 
 namespace mozilla {
diff --git a/xpcom/base/CodeAddressService.h b/xpcom/base/CodeAddressService.h
index 028c61aa3900..2050a346b06a 100644
--- a/xpcom/base/CodeAddressService.h
+++ b/xpcom/base/CodeAddressService.h
@@ -7,14 +7,15 @@
 #ifndef CodeAddressService_h__
 #define CodeAddressService_h__
 
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
 #include "mozilla/AllocPolicy.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/HashFunctions.h"
 #include "mozilla/HashTable.h"
-#include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/StackWalk.h"
-#include "mozilla/Types.h"
 
 namespace mozilla {
 
diff --git a/xpcom/base/CountingAllocatorBase.h b/xpcom/base/CountingAllocatorBase.h
index 6c4d7ab0c3be..68a405eaee2d 100644
--- a/xpcom/base/CountingAllocatorBase.h
+++ b/xpcom/base/CountingAllocatorBase.h
@@ -7,6 +7,7 @@
 #ifndef CountingAllocatorBase_h
 #define CountingAllocatorBase_h
 
+#include <cstdlib>
 #include "mozilla/Assertions.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/mozalloc.h"
diff --git a/xpcom/base/CycleCollectedJSRuntime.h b/xpcom/base/CycleCollectedJSRuntime.h
index 72db47428d0a..fa0d63559ba2 100644
--- a/xpcom/base/CycleCollectedJSRuntime.h
+++ b/xpcom/base/CycleCollectedJSRuntime.h
@@ -7,27 +7,25 @@
 #ifndef mozilla_CycleCollectedJSRuntime_h
 #define mozilla_CycleCollectedJSRuntime_h
 
-#include <queue>
-
 #include "mozilla/CycleCollectedJSContext.h"
 #include "mozilla/DeferredFinalize.h"
 #include "mozilla/HashTable.h"
-#include "mozilla/LinkedList.h"
-#include "mozilla/mozalloc.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
 #include "mozilla/SegmentedVector.h"
 #include "jsapi.h"
 #include "jsfriendapi.h"
-#include "js/TraceKind.h"
+#include "js/TypeDecls.h"
 
 #include "nsCycleCollectionParticipant.h"
 #include "nsDataHashtable.h"
 #include "nsHashKeys.h"
+#include "nsStringFwd.h"
 #include "nsTHashtable.h"
 
 class nsCycleCollectionNoteRootCallback;
 class nsIException;
-class nsIRunnable;
 class nsWrapperCache;
 
 namespace mozilla {
diff --git a/xpcom/base/HoldDropJSObjects.h b/xpcom/base/HoldDropJSObjects.h
index 0338d58c0786..8cc3c137c61f 100644
--- a/xpcom/base/HoldDropJSObjects.h
+++ b/xpcom/base/HoldDropJSObjects.h
@@ -7,11 +7,16 @@
 #ifndef mozilla_HoldDropJSObjects_h
 #define mozilla_HoldDropJSObjects_h
 
-#include "nsCycleCollectionParticipant.h"
+#include <type_traits>
+#include "nsCycleCollectionNoteChild.h"
 
 class nsISupports;
 class nsScriptObjectTracer;
 
+namespace JS {
+class Zone;
+}
+
 // Only HoldJSObjects and DropJSObjects should be called directly.
 
 namespace mozilla {
diff --git a/xpcom/base/Logging.h b/xpcom/base/Logging.h
index 05c8bad476fa..c417bdbf770b 100644
--- a/xpcom/base/Logging.h
+++ b/xpcom/base/Logging.h
@@ -7,6 +7,8 @@
 #ifndef mozilla_logging_h
 #define mozilla_logging_h
 
+#include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
 
@@ -14,7 +16,6 @@
 #include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/Likely.h"
-#include "mozilla/TimeStamp.h"
 
 // We normally have logging enabled everywhere, but measurements showed that
 // having logging enabled on Android is quite expensive (hundreds of kilobytes
@@ -40,6 +41,8 @@
 
 namespace mozilla {
 
+class TimeStamp;
+
 // While not a 100% mapping to PR_LOG's numeric values, mozilla::LogLevel does
 // maintain a direct mapping for the Disabled, Debug and Verbose levels.
 //
diff --git a/xpcom/base/MemoryInfo.h b/xpcom/base/MemoryInfo.h
index 920880bc31c3..d122f6d3775f 100644
--- a/xpcom/base/MemoryInfo.h
+++ b/xpcom/base/MemoryInfo.h
@@ -7,9 +7,10 @@
 #ifndef mozilla_MemoryInfo_h
 #define mozilla_MemoryInfo_h
 
+#include <cstddef>
+#include <cstdint>
+#include "mozilla/Attributes.h"
 #include "mozilla/EnumSet.h"
-#include "nsTArray.h"
-
 /**
  * MemoryInfo is a helper class which describes the attributes and sizes of a
  * particular region of VM memory on Windows. It roughtly corresponds to the
diff --git a/xpcom/base/MemoryMapping.h b/xpcom/base/MemoryMapping.h
index f549631b2b50..2dc61a421565 100644
--- a/xpcom/base/MemoryMapping.h
+++ b/xpcom/base/MemoryMapping.h
@@ -7,9 +7,10 @@
 #ifndef mozilla_MemoryMapping_h
 #define mozilla_MemoryMapping_h
 
+#include <cstdint>
 #include "mozilla/EnumSet.h"
-#include "nsString.h"
-#include "nsTArray.h"
+#include "nsStringFwd.h"
+#include "nsTArrayForwardDeclare.h"
 
 /**
  * MemoryMapping is a helper class which describes an entry in the Linux
diff --git a/xpcom/base/MemoryReportingProcess.h b/xpcom/base/MemoryReportingProcess.h
index 4adfb574e2fa..36410e702b46 100644
--- a/xpcom/base/MemoryReportingProcess.h
+++ b/xpcom/base/MemoryReportingProcess.h
@@ -15,6 +15,9 @@ namespace ipc {
 class FileDescriptor;
 }  // namespace ipc
 
+template <class T>
+class Maybe;
+
 // Top-level process actors should implement this to integrate with
 // nsMemoryReportManager.
 class MemoryReportingProcess {
diff --git a/xpcom/base/MemoryTelemetry.h b/xpcom/base/MemoryTelemetry.h
index 90ec329a82cd..48a5ceccbca0 100644
--- a/xpcom/base/MemoryTelemetry.h
+++ b/xpcom/base/MemoryTelemetry.h
@@ -9,7 +9,6 @@
 
 #include "mozilla/TimeStamp.h"
 #include "mozilla/Result.h"
-#include "nsIEventTarget.h"
 #include "nsIObserver.h"
 #include "nsITimer.h"
 #include "nsTArray.h"
@@ -17,6 +16,8 @@
 
 #include <functional>
 
+class nsIEventTarget;
+
 namespace mozilla {
 
 namespace ipc {
diff --git a/xpcom/base/SizeOfState.h b/xpcom/base/SizeOfState.h
index f73da0d9c7f5..2df0b24e93f5 100644
--- a/xpcom/base/SizeOfState.h
+++ b/xpcom/base/SizeOfState.h
@@ -8,7 +8,6 @@
 #define SizeOfState_h
 
 #include "mozilla/fallible.h"
-#include "mozilla/Maybe.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Unused.h"
 #include "nsTHashtable.h"
diff --git a/xpcom/base/TupleCycleCollection.h b/xpcom/base/TupleCycleCollection.h
index 55bf67094e30..215855fdd870 100644
--- a/xpcom/base/TupleCycleCollection.h
+++ b/xpcom/base/TupleCycleCollection.h
@@ -8,7 +8,9 @@
 #define TupleCycleCollection_h
 
 #include "mozilla/Tuple.h"
-#include "nsCycleCollectionTraversalCallback.h"
+#include "nsCycleCollectionNoteChild.h"
+
+class nsCycleCollectionTraversalCallback;
 
 template <typename... Elements>
 inline void ImplCycleCollectionUnlink(mozilla::Tuple<Elements...>& aField) {
diff --git a/xpcom/base/nsAlgorithm.h b/xpcom/base/nsAlgorithm.h
index 2b4b850aacdb..1c4bb0e9dce3 100644
--- a/xpcom/base/nsAlgorithm.h
+++ b/xpcom/base/nsAlgorithm.h
@@ -7,7 +7,8 @@
 #ifndef nsAlgorithm_h___
 #define nsAlgorithm_h___
 
-#include "nsCharTraits.h"  // for |nsCharSourceTraits|, |nsCharSinkTraits|
+#include <cstdint>
+#include "mozilla/Assertions.h"
 
 template <class T>
 inline T NS_ROUNDUP(const T& aA, const T& aB) {
diff --git a/xpcom/base/nsCOMPtr.h b/xpcom/base/nsCOMPtr.h
index 002a0fc526e4..23682c615557 100644
--- a/xpcom/base/nsCOMPtr.h
+++ b/xpcom/base/nsCOMPtr.h
@@ -21,7 +21,6 @@
  */
 
 #include <type_traits>
-#include <utility>
 
 #include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Assertions.h"
diff --git a/xpcom/base/nsConsoleService.cpp b/xpcom/base/nsConsoleService.cpp
index 3646d1b134cf..61fc6c613c1f 100644
--- a/xpcom/base/nsConsoleService.cpp
+++ b/xpcom/base/nsConsoleService.cpp
@@ -11,7 +11,6 @@
 
 /* Threadsafe. */
 
-#include "nsMemory.h"
 #include "nsCOMArray.h"
 #include "nsThreadUtils.h"
 
@@ -28,7 +27,6 @@
 #include "mozilla/dom/ContentParent.h"
 #include "mozilla/dom/BrowserParent.h"
 
-#include "mozilla/Preferences.h"
 #include "mozilla/SchedulerGroup.h"
 #include "mozilla/Services.h"
 
diff --git a/xpcom/base/nsConsoleService.h b/xpcom/base/nsConsoleService.h
index bc8f3840678e..a5f34e477f15 100644
--- a/xpcom/base/nsConsoleService.h
+++ b/xpcom/base/nsConsoleService.h
@@ -11,14 +11,26 @@
 #ifndef __nsconsoleservice_h__
 #define __nsconsoleservice_h__
 
-#include "mozilla/Attributes.h"
+#include <cstdint>
+#include <utility>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/LinkedList.h"
 #include "mozilla/Mutex.h"
 
+#include "MainThreadUtils.h"
+#include "nsCOMPtr.h"
 #include "nsInterfaceHashtable.h"
 #include "nsHashKeys.h"
 
+#include "nsIConsoleListener.h"
+#include "nsIConsoleMessage.h"
 #include "nsIConsoleService.h"
 #include "nsIObserver.h"
+#include "nsISupports.h"
+
+template <class T>
+class nsCOMArray;
 
 class nsConsoleService final : public nsIConsoleService, public nsIObserver {
  public:
diff --git a/xpcom/base/nsCycleCollectionNoteRootCallback.h b/xpcom/base/nsCycleCollectionNoteRootCallback.h
index e1c011851e02..21dc89394ad0 100644
--- a/xpcom/base/nsCycleCollectionNoteRootCallback.h
+++ b/xpcom/base/nsCycleCollectionNoteRootCallback.h
@@ -7,8 +7,15 @@
 #ifndef nsCycleCollectionNoteRootCallback_h__
 #define nsCycleCollectionNoteRootCallback_h__
 
+#include "nscore.h"
+
 class nsCycleCollectionParticipant;
 class nsISupports;
+class JSObject;
+
+namespace JS {
+class GCCellPtr;
+}
 
 class nsCycleCollectionNoteRootCallback {
  public:
diff --git a/xpcom/base/nsCycleCollector.cpp b/xpcom/base/nsCycleCollector.cpp
index f9552a868113..8246b0ee2c34 100644
--- a/xpcom/base/nsCycleCollector.cpp
+++ b/xpcom/base/nsCycleCollector.cpp
@@ -166,6 +166,7 @@
 #include <utility>
 
 #include "GeckoProfiler.h"
+#include "js/SliceBudget.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/AutoGlobalTimelineMarker.h"
 #include "mozilla/Likely.h"
diff --git a/xpcom/base/nsCycleCollector.h b/xpcom/base/nsCycleCollector.h
index 18cb7dcd4df1..0ecdd7393eb0 100644
--- a/xpcom/base/nsCycleCollector.h
+++ b/xpcom/base/nsCycleCollector.h
@@ -13,11 +13,12 @@ class nsISupports;
 template <class T>
 struct already_AddRefed;
 
-#include "nsError.h"
-#include "nsID.h"
-
+#include <cstdint>
 #include "mozilla/Attributes.h"
-#include "js/SliceBudget.h"
+
+namespace js {
+class SliceBudget;
+}
 
 namespace mozilla {
 class CycleCollectedJSContext;
diff --git a/xpcom/base/nsError.h b/xpcom/base/nsError.h
index d72fe79bfb3a..040cd4612c2d 100644
--- a/xpcom/base/nsError.h
+++ b/xpcom/base/nsError.h
@@ -19,7 +19,7 @@
 #define NS_ERROR_SEVERITY_SUCCESS 0
 #define NS_ERROR_SEVERITY_ERROR 1
 
-#include "ErrorList.h"
+#include "ErrorList.h"  // IWYU pragma: export
 
 /**
  * @name Standard Error Handling Macros
diff --git a/xpcom/base/nsMemory.h b/xpcom/base/nsMemory.h
index 6c07fb8f12bc..b64b7b66be06 100644
--- a/xpcom/base/nsMemory.h
+++ b/xpcom/base/nsMemory.h
@@ -7,7 +7,7 @@
 #ifndef nsMemory_h__
 #define nsMemory_h__
 
-#include "nsXPCOM.h"
+#include "nsError.h"
 
 class nsIMemory;
 
diff --git a/xpcom/base/nsMemoryReporterManager.cpp b/xpcom/base/nsMemoryReporterManager.cpp
index ad8c45cf0849..c8322db99b2b 100644
--- a/xpcom/base/nsMemoryReporterManager.cpp
+++ b/xpcom/base/nsMemoryReporterManager.cpp
@@ -4,13 +4,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#include "nsMemoryReporterManager.h"
+
 #include "nsAtomTable.h"
 #include "nsCOMPtr.h"
 #include "nsCOMArray.h"
 #include "nsPrintfCString.h"
 #include "nsProxyRelease.h"
 #include "nsServiceManagerUtils.h"
-#include "nsMemoryReporterManager.h"
 #include "nsITimer.h"
 #include "nsThreadUtils.h"
 #include "nsPIDOMWindow.h"
diff --git a/xpcom/base/nsMemoryReporterManager.h b/xpcom/base/nsMemoryReporterManager.h
index f827f25b99ae..a60ec9227407 100644
--- a/xpcom/base/nsMemoryReporterManager.h
+++ b/xpcom/base/nsMemoryReporterManager.h
@@ -10,11 +10,9 @@
 #include "mozilla/Mutex.h"
 #include "nsDataHashtable.h"
 #include "nsHashKeys.h"
-#include "nsIEventTarget.h"
 #include "nsIMemoryReporter.h"
-#include "nsITimer.h"
+#include "nsISupports.h"
 #include "nsServiceManagerUtils.h"
-#include "nsDataHashtable.h"
 
 #ifdef XP_WIN
 #  include <windows.h>
@@ -27,6 +25,9 @@ class MemoryReport;
 }  // namespace dom
 }  // namespace mozilla
 
+class mozIDOMWindowProxy;
+class nsIEventTarget;
+class nsIRunnable;
 class nsITimer;
 
 class nsMemoryReporterManager final : public nsIMemoryReporterManager,
diff --git a/xpcom/base/nsSystemInfo.h b/xpcom/base/nsSystemInfo.h
index 58881ae51e30..6d12c8e34db2 100644
--- a/xpcom/base/nsSystemInfo.h
+++ b/xpcom/base/nsSystemInfo.h
@@ -10,12 +10,13 @@
 #include "nsHashPropertyBag.h"
 #include "nsISystemInfo.h"
 #include "mozilla/MozPromise.h"
-#include "mozilla/LazyIdleThread.h"
 
 #ifdef MOZ_WIDGET_ANDROID
 #  include "mozilla/dom/PContent.h"
 #endif  // MOZ_WIDGET_ANDROID
 
+class nsISerialEventTarget;
+
 struct FolderDiskInfo {
   nsCString model;
   nsCString revision;
diff --git a/xpcom/base/nscore.h b/xpcom/base/nscore.h
index 6392e495585a..f7baacd79861 100644
--- a/xpcom/base/nscore.h
+++ b/xpcom/base/nscore.h
@@ -12,7 +12,7 @@
  * c++ definitions needed by nscore.h
  */
 #ifndef _XPCOM_CONFIG_H_
-#  include "xpcom-config.h"
+#  include "xpcom-config.h"  // IWYU pragma: export
 #endif
 
 /* Definitions of functions and operators that allocate memory. */
@@ -23,10 +23,10 @@
 /**
  * Incorporate the integer data types which XPCOM uses.
  */
-#include <stddef.h>
-#include <stdint.h>
+#include <stddef.h>  // IWYU pragma: export
+#include <stdint.h>  // IWYU pragma: export
 
-#include "mozilla/HelperMacros.h"
+#include "mozilla/HelperMacros.h"  // IWYU pragma: export
 #include "mozilla/RefCountType.h"
 
 /* Core XPCOM declarations. */
@@ -200,7 +200,7 @@
 /**
  * Generic XPCOM result data type
  */
-#include "nsError.h"
+#include "nsError.h"  // IWYU pragma: export
 
 typedef MozRefCountType nsrefcnt;
 
diff --git a/xpcom/build/nsXULAppAPI.h b/xpcom/build/nsXULAppAPI.h
index 695583233749..a143bb10be9d 100644
--- a/xpcom/build/nsXULAppAPI.h
+++ b/xpcom/build/nsXULAppAPI.h
@@ -7,25 +7,31 @@
 #ifndef _nsXULAppAPI_h__
 #define _nsXULAppAPI_h__
 
-#include "nsID.h"
-#include "xrecore.h"
-#include "nsXPCOM.h"
-#include "nsISupports.h"
-#include "mozilla/Logging.h"
-#include "mozilla/XREAppData.h"
 #include "js/TypeDecls.h"
-
 #include "mozilla/ArrayUtils.h"
-#include "mozilla/Assertions.h"
-#include "mozilla/Vector.h"
 #include "mozilla/TimeStamp.h"
-#include "XREChildData.h"
-#include "XREShellData.h"
+#include "nscore.h"
+#include "xrecore.h"
 
 #if defined(MOZ_WIDGET_ANDROID)
 #  include <jni.h>
 #endif
 
+class JSString;
+class MessageLoop;
+class nsIDirectoryServiceProvider;
+class nsIFile;
+class nsISupports;
+struct JSContext;
+struct XREChildData;
+struct XREShellData;
+
+namespace mozilla {
+class XREAppData;
+struct BootstrapConfig;
+struct Module;
+}  // namespace mozilla
+
 /**
  * A directory service key which provides the platform-correct "application
  * data" directory as follows, where $name and $vendor are as defined above and
@@ -205,9 +211,6 @@
  * @note           If the binary is linked against the standalone XPCOM glue,
  *                 XPCOMGlueStartup() should be called before this method.
  */
-namespace mozilla {
-struct BootstrapConfig;
-}
 XRE_API(int, XRE_main,
         (int argc, char* argv[], const mozilla::BootstrapConfig& aConfig))
 
@@ -454,8 +457,6 @@ XRE_API(nsresult, XRE_InitCommandLine, (int aArgc, char* aArgv[]))
 
 XRE_API(nsresult, XRE_DeinitCommandLine, ())
 
-class MessageLoop;
-
 XRE_API(void, XRE_ShutdownChildProcess, ())
 
 XRE_API(MessageLoop*, XRE_GetIOMessageLoop, ())
diff --git a/xpcom/ds/ArenaAllocator.h b/xpcom/ds/ArenaAllocator.h
index 51c08f29365a..76498986ce4f 100644
--- a/xpcom/ds/ArenaAllocator.h
+++ b/xpcom/ds/ArenaAllocator.h
@@ -9,7 +9,6 @@
 
 #include <algorithm>
 #include <cstdint>
-#include <sstream>
 
 #include "mozilla/Assertions.h"
 #include "mozilla/fallible.h"
diff --git a/xpcom/ds/PLDHashTable.h b/xpcom/ds/PLDHashTable.h
index d28186c760b2..8b9097882bce 100644
--- a/xpcom/ds/PLDHashTable.h
+++ b/xpcom/ds/PLDHashTable.h
@@ -12,12 +12,10 @@
 
 #include <utility>
 
+#include "mozilla/Assertions.h"
 #include "mozilla/Atomics.h"
-#include "mozilla/Attributes.h"  // for MOZ_ALWAYS_INLINE
-#include "mozilla/FunctionTypeTraits.h"
 #include "mozilla/HashFunctions.h"
 #include "mozilla/MemoryReporting.h"
-#include "mozilla/Types.h"
 #include "mozilla/fallible.h"
 #include "nscore.h"
 
diff --git a/xpcom/ds/nsAtom.h b/xpcom/ds/nsAtom.h
index f17bba09b6c1..240e9ffcb0c2 100644
--- a/xpcom/ds/nsAtom.h
+++ b/xpcom/ds/nsAtom.h
@@ -9,10 +9,11 @@
 
 #include <type_traits>
 
-#include "nsISupportsImpl.h"
-#include "nsString.h"
 #include "mozilla/Atomics.h"
-#include "mozilla/UniquePtr.h"
+#include "mozilla/Char16.h"
+#include "mozilla/MemoryReporting.h"
+#include "nsISupports.h"
+#include "nsString.h"
 
 namespace mozilla {
 struct AtomsSizes;
diff --git a/xpcom/ds/nsCharSeparatedTokenizer.h b/xpcom/ds/nsCharSeparatedTokenizer.h
index d1c22c9674f4..7685fb7681c4 100644
--- a/xpcom/ds/nsCharSeparatedTokenizer.h
+++ b/xpcom/ds/nsCharSeparatedTokenizer.h
@@ -10,7 +10,7 @@
 #include "mozilla/RangedPtr.h"
 
 #include "nsDependentSubstring.h"
-#include "nsCRT.h"
+#include "nsCRTGlue.h"
 
 /**
  * This parses a SeparatorChar-separated string into tokens.
diff --git a/xpcom/ds/nsDeque.h b/xpcom/ds/nsDeque.h
index cff3b5739bd4..7cec06602917 100644
--- a/xpcom/ds/nsDeque.h
+++ b/xpcom/ds/nsDeque.h
@@ -28,11 +28,9 @@
 
 #include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Assertions.h"
-#include "mozilla/Attributes.h"
 #include "mozilla/fallible.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/RefPtr.h"
-#include "nscore.h"
 #include "nsDebug.h"
 #include "nsISupports.h"
 
diff --git a/xpcom/ds/nsExpirationTracker.h b/xpcom/ds/nsExpirationTracker.h
index 0906f3c0b825..a5100b3bd5d9 100644
--- a/xpcom/ds/nsExpirationTracker.h
+++ b/xpcom/ds/nsExpirationTracker.h
@@ -7,16 +7,25 @@
 #ifndef NSEXPIRATIONTRACKER_H_
 #define NSEXPIRATIONTRACKER_H_
 
-#include "mozilla/Logging.h"
+#include <cstring>
+#include "MainThreadUtils.h"
+#include "nsAlgorithm.h"
+#include "nsDebug.h"
 #include "nsTArray.h"
 #include "nsITimer.h"
 #include "nsCOMPtr.h"
-#include "nsComponentManagerUtils.h"
 #include "nsIEventTarget.h"
 #include "nsIObserver.h"
 #include "nsIObserverService.h"
+#include "nsISupports.h"
+#include "nsIThread.h"
 #include "nsThreadUtils.h"
-#include "mozilla/Attributes.h"
+#include "nscore.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/Likely.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefCountType.h"
+#include "mozilla/RefPtr.h"
 #include "mozilla/Services.h"
 
 /**
diff --git a/xpcom/ds/nsObserverList.h b/xpcom/ds/nsObserverList.h
index b3c32a1fd750..9f209e40d662 100644
--- a/xpcom/ds/nsObserverList.h
+++ b/xpcom/ds/nsObserverList.h
@@ -8,7 +8,6 @@
 #define nsObserverList_h___
 
 #include "nsISupports.h"
-#include "nsCOMPtr.h"
 #include "nsCOMArray.h"
 #include "nsIObserver.h"
 #include "nsHashKeys.h"
diff --git a/xpcom/ds/nsObserverService.h b/xpcom/ds/nsObserverService.h
index 389bc7ac05e8..b616be936597 100644
--- a/xpcom/ds/nsObserverService.h
+++ b/xpcom/ds/nsObserverService.h
@@ -21,8 +21,6 @@
     }                                               \
   }
 
-class nsIMemoryReporter;
-
 class nsObserverService final : public nsIObserverService,
                                 public nsIMemoryReporter {
  public:
diff --git a/xpcom/ds/nsTObserverArray.h b/xpcom/ds/nsTObserverArray.h
index 691294c6f8f1..eec33957255d 100644
--- a/xpcom/ds/nsTObserverArray.h
+++ b/xpcom/ds/nsTObserverArray.h
@@ -12,8 +12,6 @@
 #include "nsTArray.h"
 #include "nsCycleCollectionNoteChild.h"
 
-#include <functional>
-
 /**
  * An array of observers. Like a normal array, but supports iterators that are
  * stable even if the array is modified during iteration.
diff --git a/xpcom/ds/nsTPriorityQueue.h b/xpcom/ds/nsTPriorityQueue.h
index f1052f9de1de..1fa1cc1e50db 100644
--- a/xpcom/ds/nsTPriorityQueue.h
+++ b/xpcom/ds/nsTPriorityQueue.h
@@ -7,8 +7,8 @@
 #ifndef NS_TPRIORITY_QUEUE_H_
 #define NS_TPRIORITY_QUEUE_H_
 
+#include "mozilla/Assertions.h"
 #include "nsTArray.h"
-#include "nsDebug.h"
 
 /**
  * A templatized priority queue data structure that uses an nsTArray to serve as
diff --git a/xpcom/ds/nsWhitespaceTokenizer.h b/xpcom/ds/nsWhitespaceTokenizer.h
index 99ecc8afaa03..77fea708504b 100644
--- a/xpcom/ds/nsWhitespaceTokenizer.h
+++ b/xpcom/ds/nsWhitespaceTokenizer.h
@@ -9,7 +9,7 @@
 
 #include "mozilla/RangedPtr.h"
 #include "nsDependentSubstring.h"
-#include "nsCRT.h"
+#include "nsCRTGlue.h"
 
 template <typename DependentSubstringType, bool IsWhitespace(char16_t)>
 class nsTWhitespaceTokenizer {
diff --git a/xpcom/threads/AbstractThread.h b/xpcom/threads/AbstractThread.h
index 227bd75b76b7..ef339986ddf9 100644
--- a/xpcom/threads/AbstractThread.h
+++ b/xpcom/threads/AbstractThread.h
@@ -7,13 +7,15 @@
 #if !defined(AbstractThread_h_)
 #  define AbstractThread_h_
 
-#  include "mozilla/RefPtr.h"
+#  include "mozilla/AlreadyAddRefed.h"
 #  include "mozilla/ThreadLocal.h"
 #  include "nscore.h"
-#  include "nsIRunnable.h"
 #  include "nsISerialEventTarget.h"
-#  include "nsISupportsImpl.h"
-#  include "nsIThread.h"
+#  include "nsISupports.h"
+
+class nsIEventTarget;
+class nsIRunnable;
+class nsIThread;
 
 namespace mozilla {
 
diff --git a/xpcom/threads/BlockingResourceBase.h b/xpcom/threads/BlockingResourceBase.h
index 6c8039c8f406..b5501599f159 100644
--- a/xpcom/threads/BlockingResourceBase.h
+++ b/xpcom/threads/BlockingResourceBase.h
@@ -7,13 +7,13 @@
 #ifndef mozilla_BlockingResourceBase_h
 #define mozilla_BlockingResourceBase_h
 
-#include "mozilla/Logging.h"
+#include "mozilla/MemoryReporting.h"
 #include "mozilla/ThreadLocal.h"
 
 #include "nscore.h"
 #include "nsDebug.h"
-#include "nsError.h"
-#include "nsISupportsImpl.h"
+
+#include "prtypes.h"
 
 #ifdef DEBUG
 
@@ -22,13 +22,11 @@
 
 #  include "prinit.h"
 
-#  include "nsString.h"
-
 #  ifndef MOZ_CALLSTACK_DISABLED
+#    include "mozilla/Maybe.h"
 #    include "nsTArray.h"
 #  endif
 
-#  include "nsXPCOM.h"
 #endif
 
 //
diff --git a/xpcom/threads/CPUUsageWatcher.h b/xpcom/threads/CPUUsageWatcher.h
index cf3f50b154d9..c3a643378a4c 100644
--- a/xpcom/threads/CPUUsageWatcher.h
+++ b/xpcom/threads/CPUUsageWatcher.h
@@ -10,7 +10,6 @@
 #include <stdint.h>
 
 #include "mozilla/HangAnnotations.h"
-#include "mozilla/BackgroundHangMonitor.h"
 #include "mozilla/Result.h"
 
 // We only support OSX and Windows, because on Linux we're forced to read
diff --git a/xpcom/threads/InputEventStatistics.h b/xpcom/threads/InputEventStatistics.h
index c90f73767c6f..e5531302b5dc 100644
--- a/xpcom/threads/InputEventStatistics.h
+++ b/xpcom/threads/InputEventStatistics.h
@@ -7,10 +7,8 @@
 #if !defined(InputEventStatistics_h_)
 #  define InputEventStatistics_h_
 
-#  include "mozilla/ClearOnShutdown.h"
-#  include "mozilla/Maybe.h"
-#  include "mozilla/Preferences.h"
 #  include "mozilla/TimeStamp.h"
+#  include "mozilla/UniquePtr.h"
 #  include "nsTArray.h"
 
 namespace mozilla {
diff --git a/xpcom/threads/LazyIdleThread.h b/xpcom/threads/LazyIdleThread.h
index f0f60f5bb3ec..43a660b92f5e 100644
--- a/xpcom/threads/LazyIdleThread.h
+++ b/xpcom/threads/LazyIdleThread.h
@@ -18,7 +18,7 @@
 
 #include "mozilla/Mutex.h"
 #include "nsCOMPtr.h"
-#include "nsTArray.h"
+#include "nsTArrayForwardDeclare.h"
 #include "nsString.h"
 #include "mozilla/Attributes.h"
 
diff --git a/xpcom/threads/MozPromise.h b/xpcom/threads/MozPromise.h
index 8cd8ae93330f..2f6245a9ccc9 100644
--- a/xpcom/threads/MozPromise.h
+++ b/xpcom/threads/MozPromise.h
@@ -15,7 +15,6 @@
 #  include "mozilla/Monitor.h"
 #  include "mozilla/Mutex.h"
 #  include "mozilla/RefPtr.h"
-#  include "mozilla/Tuple.h"
 #  include "mozilla/UniquePtr.h"
 #  include "mozilla/Variant.h"
 #  include "nsIDirectTaskDispatcher.h"
diff --git a/xpcom/threads/Mutex.h b/xpcom/threads/Mutex.h
index 0fa6e1700921..e6d58806c9ca 100644
--- a/xpcom/threads/Mutex.h
+++ b/xpcom/threads/Mutex.h
@@ -9,6 +9,7 @@
 
 #include "mozilla/BlockingResourceBase.h"
 #include "mozilla/PlatformMutex.h"
+#include "nsISupports.h"
 
 //
 // Provides:
diff --git a/xpcom/threads/SchedulerGroup.h b/xpcom/threads/SchedulerGroup.h
index 342cbc69452c..7221ce3bb752 100644
--- a/xpcom/threads/SchedulerGroup.h
+++ b/xpcom/threads/SchedulerGroup.h
@@ -7,17 +7,15 @@
 #ifndef mozilla_SchedulerGroup_h
 #define mozilla_SchedulerGroup_h
 
-#include "mozilla/EventQueue.h"
-#include "mozilla/AlreadyAddRefed.h"
-#include "mozilla/LinkedList.h"
-#include "mozilla/Queue.h"
+#include "mozilla/RefPtr.h"
 #include "mozilla/TaskCategory.h"
-#include "mozilla/ThreadLocal.h"
-#include "mozilla/ThrottledEventQueue.h"
-#include "mozilla/TimeStamp.h"
 #include "nsCOMPtr.h"
-#include "nsISupportsImpl.h"
+#include "nsID.h"
+#include "nsIRunnable.h"
+#include "nsISupports.h"
+#include "nsStringFwd.h"
 #include "nsThreadUtils.h"
+#include "nscore.h"
 
 class nsIEventTarget;
 class nsIRunnable;
diff --git a/xpcom/threads/SharedThreadPool.h b/xpcom/threads/SharedThreadPool.h
index 86c9b751e6db..936cac5cd8bb 100644
--- a/xpcom/threads/SharedThreadPool.h
+++ b/xpcom/threads/SharedThreadPool.h
@@ -7,13 +7,17 @@
 #ifndef SharedThreadPool_h_
 #define SharedThreadPool_h_
 
-#include <queue>
-#include "mozilla/RefPtr.h"
-#include "nsThreadUtils.h"
-#include "nsIThreadPool.h"
-#include "nsISupports.h"
-#include "nsISupportsImpl.h"
+#include <utility>
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/RefCountType.h"
 #include "nsCOMPtr.h"
+#include "nsID.h"
+#include "nsIEventTarget.h"
+#include "nsIThreadPool.h"
+#include "nsString.h"
+#include "nscore.h"
+
+class nsIRunnable;
 
 namespace mozilla {
 
diff --git a/xpcom/threads/StateMirroring.h b/xpcom/threads/StateMirroring.h
index b5dfc5602ba9..c233116962d9 100644
--- a/xpcom/threads/StateMirroring.h
+++ b/xpcom/threads/StateMirroring.h
@@ -7,15 +7,19 @@
 #if !defined(StateMirroring_h_)
 #  define StateMirroring_h_
 
-#  include "mozilla/Maybe.h"
-#  include "mozilla/MozPromise.h"
-#  include "mozilla/StateWatching.h"
-#  include "mozilla/TaskDispatcher.h"
-#  include "mozilla/UniquePtr.h"
-#  include "mozilla/Unused.h"
-
+#  include <cstddef>
+#  include "mozilla/AbstractThread.h"
+#  include "mozilla/AlreadyAddRefed.h"
+#  include "mozilla/Assertions.h"
 #  include "mozilla/Logging.h"
-#  include "nsISupportsImpl.h"
+#  include "mozilla/Maybe.h"
+#  include "mozilla/RefPtr.h"
+#  include "mozilla/StateWatching.h"
+#  include "nsCOMPtr.h"
+#  include "nsIRunnable.h"
+#  include "nsISupports.h"
+#  include "nsTArray.h"
+#  include "nsThreadUtils.h"
 
 /*
  * The state-mirroring machinery allows pieces of interesting state to be
diff --git a/xpcom/threads/StateWatching.h b/xpcom/threads/StateWatching.h
index 71381a609661..3da0c63bfeef 100644
--- a/xpcom/threads/StateWatching.h
+++ b/xpcom/threads/StateWatching.h
@@ -7,13 +7,16 @@
 #if !defined(StateWatching_h_)
 #  define StateWatching_h_
 
+#  include <cstddef>
+#  include <new>
+#  include <utility>
 #  include "mozilla/AbstractThread.h"
+#  include "mozilla/Assertions.h"
 #  include "mozilla/Logging.h"
-#  include "mozilla/TaskDispatcher.h"
-#  include "mozilla/UniquePtr.h"
-#  include "mozilla/Unused.h"
-
-#  include "nsISupportsImpl.h"
+#  include "mozilla/RefPtr.h"
+#  include "nsISupports.h"
+#  include "nsTArray.h"
+#  include "nsThreadUtils.h"
 
 /*
  * The state-watching machinery automates the process of responding to changes
diff --git a/xpcom/threads/TaskDispatcher.h b/xpcom/threads/TaskDispatcher.h
index f2f3cf8bad1d..558221aa9589 100644
--- a/xpcom/threads/TaskDispatcher.h
+++ b/xpcom/threads/TaskDispatcher.h
@@ -12,7 +12,6 @@
 #  include "mozilla/AbstractThread.h"
 #  include "mozilla/Maybe.h"
 #  include "mozilla/UniquePtr.h"
-#  include "mozilla/Unused.h"
 #  include "nsIDirectTaskDispatcher.h"
 #  include "nsISupportsImpl.h"
 #  include "nsTArray.h"
diff --git a/xpcom/threads/TaskQueue.h b/xpcom/threads/TaskQueue.h
index ce039bef9bc2..5b9837ecbd53 100644
--- a/xpcom/threads/TaskQueue.h
+++ b/xpcom/threads/TaskQueue.h
@@ -15,7 +15,6 @@
 #include "mozilla/MozPromise.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/TaskDispatcher.h"
-#include "mozilla/Unused.h"
 #include "nsIDirectTaskDispatcher.h"
 #include "nsThreadUtils.h"
 
diff --git a/xpcom/threads/nsProcess.h b/xpcom/threads/nsProcess.h
index bf1e8ca0f1c4..c7cd0a3d055f 100644
--- a/xpcom/threads/nsProcess.h
+++ b/xpcom/threads/nsProcess.h
@@ -14,8 +14,6 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/Mutex.h"
 #include "nsIProcess.h"
-#include "nsIFile.h"
-#include "nsIObserver.h"
 #include "nsIObserver.h"
 #include "nsMaybeWeakPtr.h"
 #include "nsString.h"
@@ -34,6 +32,8 @@
     }                                                \
   }
 
+class nsIFile;
+
 class nsProcess final : public nsIProcess, public nsIObserver {
  public:
   NS_DECL_THREADSAFE_ISUPPORTS
diff --git a/xpcom/threads/nsProxyRelease.h b/xpcom/threads/nsProxyRelease.h
index b494706ba9c2..0c132d362bb6 100644
--- a/xpcom/threads/nsProxyRelease.h
+++ b/xpcom/threads/nsProxyRelease.h
@@ -14,6 +14,7 @@
 #include "mozilla/Unused.h"
 #include "nsCOMPtr.h"
 #include "nsIEventTarget.h"
+#include "nsISerialEventTarget.h"
 #include "nsIThread.h"
 #include "nsPrintfCString.h"
 #include "nsThreadUtils.h"
@@ -22,6 +23,8 @@
 #  error NS_ProxyRelease implementation depends on NSPR.
 #endif
 
+class nsIRunnable;
+
 namespace detail {
 
 template <typename T>
diff --git a/xpcom/threads/nsThread.h b/xpcom/threads/nsThread.h
index bf85fb2460e1..305f092dbaa8 100644
--- a/xpcom/threads/nsThread.h
+++ b/xpcom/threads/nsThread.h
@@ -7,37 +7,41 @@
 #ifndef nsThread_h__
 #define nsThread_h__
 
+#include "MainThreadUtils.h"
 #include "mozilla/AlreadyAddRefed.h"
-#include "mozilla/Array.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/IntegerTypeTraits.h"
+#include "mozilla/EventQueue.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Mutex.h"
 #include "mozilla/NotNull.h"
-#include "mozilla/SynchronizedEventQueue.h"
+#include "mozilla/PerformanceCounter.h"
+#include "mozilla/RefPtr.h"
 #include "mozilla/TaskDispatcher.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/UniquePtr.h"
-#include "mozilla/dom/DocGroup.h"
 #include "nsIDirectTaskDispatcher.h"
+#include "nsIEventTarget.h"
+#include "nsISerialEventTarget.h"
 #include "nsISupportsPriority.h"
+#include "nsIThread.h"
 #include "nsIThreadInternal.h"
-#include "nsString.h"
-#include "nsTObserverArray.h"
-#include "nsThreadUtils.h"
-#include "prenv.h"
+#include "nsTArray.h"
 
 namespace mozilla {
 class CycleCollectedJSContext;
-class EventQueue;
+class SynchronizedEventQueue;
 class ThreadEventQueue;
 class ThreadEventTarget;
+
+template <typename T, size_t Length>
+class Array;
 }  // namespace mozilla
 
 using mozilla::NotNull;
 
+class nsIRunnable;
 class nsLocalExecutionRecord;
 class nsThreadEnumerator;
 
@@ -377,8 +381,6 @@ struct nsThreadShutdownContext {
   bool mIsMainThreadJoining;
 };
 
-class nsLocalExecutionRecord;
-
 // This RAII class controls the duration of the associated nsThread's local
 // execution mode and provides access to the local event target. (See
 // nsThread::EnterLocalExecution() for details.) It is constructed from an
diff --git a/xpcom/threads/nsThreadManager.h b/xpcom/threads/nsThreadManager.h
index c85e936ed21c..fa223702aaa7 100644
--- a/xpcom/threads/nsThreadManager.h
+++ b/xpcom/threads/nsThreadManager.h
@@ -7,12 +7,18 @@
 #ifndef nsThreadManager_h__
 #define nsThreadManager_h__
 
-#include "mozilla/Mutex.h"
-#include "mozilla/TaskController.h"
 #include "nsIThreadManager.h"
 #include "nsThread.h"
 
 class nsIRunnable;
+class nsIEventTarget;
+class nsISerialEventTarget;
+class nsIThread;
+
+namespace mozilla {
+class IdleTaskManager;
+class SynchronizedEventQueue;
+}  // namespace mozilla
 
 class BackgroundEventTarget;
 
diff --git a/xpcom/threads/nsThreadPool.h b/xpcom/threads/nsThreadPool.h
index 2606eb33e01f..7bdafde57c66 100644
--- a/xpcom/threads/nsThreadPool.h
+++ b/xpcom/threads/nsThreadPool.h
@@ -8,17 +8,17 @@
 #define nsThreadPool_h__
 
 #include "nsIThreadPool.h"
-#include "nsIThread.h"
 #include "nsIRunnable.h"
 #include "nsCOMArray.h"
 #include "nsCOMPtr.h"
 #include "nsThreadUtils.h"
 #include "mozilla/Atomics.h"
-#include "mozilla/Attributes.h"
 #include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/CondVar.h"
 #include "mozilla/EventQueue.h"
 #include "mozilla/Mutex.h"
-#include "mozilla/Monitor.h"
+
+class nsIThread;
 
 class nsThreadPool final : public mozilla::Runnable, public nsIThreadPool {
  public:
diff --git a/xpcom/threads/nsTimerImpl.h b/xpcom/threads/nsTimerImpl.h
index bf659478eacd..30bcc76ed3b7 100644
--- a/xpcom/threads/nsTimerImpl.h
+++ b/xpcom/threads/nsTimerImpl.h
@@ -14,7 +14,6 @@
 #include "nsCOMPtr.h"
 
 #include "mozilla/Attributes.h"
-#include "mozilla/Logging.h"
 #include "mozilla/Mutex.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/Variant.h"
@@ -32,8 +31,13 @@ extern mozilla::LogModule* GetTimerLog();
     }                                                \
   }
 
+class nsIObserver;
 class nsTimerImplHolder;
 
+namespace mozilla {
+class LogModule;
+}
+
 // TimerThread, nsTimerEvent, and nsTimer have references to these. nsTimer has
 // a separate lifecycle so we can Cancel() the underlying timer when the user of
 // the nsTimer has let go of its last reference.