From d10d03d07698ba2c7ec5b63e832feb6ec1fa6641 Mon Sep 17 00:00:00 2001
From: Simon Giesecke <sgiesecke@mozilla.com>
Date: Mon, 23 Nov 2020 16:10:41 +0000
Subject: [PATCH] Bug 1676365 - Move SpinEventLoopUntil to separate header.
 r=#xpcom-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D96556

Depends on D96554
---
 devtools/platform/nsJSInspector.cpp           |   2 +-
 dom/base/nsGlobalWindowInner.cpp              |   1 +
 dom/base/nsGlobalWindowOuter.cpp              |   1 +
 dom/cache/Manager.cpp                         |   1 +
 dom/filehandle/ActorsParent.cpp               |   1 +
 dom/indexedDB/ActorsParent.cpp                |   1 +
 dom/ipc/ContentChild.cpp                      |   1 +
 dom/localstorage/ActorsParent.cpp             |   1 +
 dom/localstorage/LSObject.cpp                 |   1 +
 dom/media/fuzz/FuzzMedia.cpp                  |   1 +
 dom/media/gmp/GMPServiceParent.cpp            |   1 +
 dom/media/gtest/GMPTestMonitor.h              |   1 +
 dom/media/gtest/TestAudioTrackGraph.cpp       |   1 +
 dom/media/gtest/TestCDMStorage.cpp            |   1 +
 dom/media/gtest/TestDriftCompensation.cpp     |   1 +
 dom/media/gtest/TestMediaDataDecoder.cpp      |   1 +
 dom/media/gtest/TestMediaDataEncoder.cpp      |   1 +
 dom/plugins/base/nsPluginHost.cpp             |   1 +
 dom/quota/ActorsParent.cpp                    |   1 +
 dom/simpledb/ActorsParent.cpp                 |   1 +
 dom/storage/StorageObserver.cpp               |   1 +
 dom/xhr/XMLHttpRequestMainThread.cpp          |   1 +
 .../pref/autoconfig/src/nsAutoConfig.cpp      |   1 +
 gfx/layers/ipc/CompositorBridgeChild.cpp      |   1 +
 gfx/layers/ipc/CompositorThread.cpp           |   1 +
 ipc/glue/BackgroundImpl.cpp                   |   1 +
 layout/base/nsDocumentViewer.cpp              |   1 +
 layout/printing/ipc/RemotePrintJobChild.cpp   |   1 +
 .../gtest/mediapipeline_unittest.cpp          |   1 +
 modules/libpref/Preferences.cpp               |   1 +
 netwerk/base/ProxyAutoConfig.cpp              |   1 +
 netwerk/base/nsAsyncRedirectVerifyHelper.cpp  |   1 +
 netwerk/base/nsSyncStreamListener.cpp         |   1 +
 netwerk/protocol/http/nsHttpConnectionMgr.cpp |   1 +
 netwerk/test/fuzz/FuzzingStreamListener.h     |   2 +-
 netwerk/test/fuzz/TestFtpFuzzing.cpp          |   1 +
 netwerk/test/fuzz/TestHttpFuzzing.cpp         |   1 +
 netwerk/test/fuzz/TestWebsocketFuzzing.cpp    |   1 +
 .../test/gtest/TestBufferedInputStream.cpp    |   1 +
 netwerk/test/gtest/TestCommon.h               |   1 +
 netwerk/test/gtest/TestMIMEInputStream.cpp    |   1 +
 .../TestPartiallySeekableInputStream.cpp      |   1 +
 storage/mozStorageConnection.cpp              |   1 +
 storage/mozStorageService.cpp                 |   1 +
 toolkit/components/places/Database.cpp        |   1 +
 .../places/tests/gtest/places_test_harness.h  |   1 +
 .../places/tests/gtest/test_IHistory.cpp      |   1 +
 .../printingui/ipc/nsPrintingProxy.cpp        |   1 +
 .../url-classifier/tests/gtest/Common.cpp     |   1 +
 toolkit/xre/ProfileReset.cpp                  |   1 +
 .../preload/gtest/TestFetchPreloader.cpp      |   1 +
 widget/windows/nsDataObj.cpp                  |   1 +
 xpcom/base/AppShutdown.cpp                    |   1 +
 xpcom/tests/gtest/TestEventPriorities.cpp     |   1 +
 .../gtest/TestInputStreamLengthHelper.cpp     |   1 +
 .../tests/gtest/TestMultiplexInputStream.cpp  |   1 +
 .../gtest/TestNonBlockingAsyncInputStream.cpp |   1 +
 xpcom/tests/gtest/TestSlicedInputStream.cpp   |   1 +
 xpcom/tests/gtest/TestThreadUtils.cpp         |   1 +
 xpcom/threads/SharedThreadPool.cpp            |   1 +
 xpcom/threads/SpinEventLoopUntil.h            | 108 ++++++++++++++++++
 xpcom/threads/ThreadEventTarget.cpp           |   1 +
 xpcom/threads/moz.build                       |   1 +
 xpcom/threads/nsThread.cpp                    |   1 +
 xpcom/threads/nsThreadManager.cpp             |   1 +
 xpcom/threads/nsThreadPool.cpp                |   1 +
 xpcom/threads/nsThreadUtils.h                 |  94 +--------------
 xpfe/appshell/AppWindow.cpp                   |   1 +
 68 files changed, 175 insertions(+), 95 deletions(-)
 create mode 100644 xpcom/threads/SpinEventLoopUntil.h

diff --git a/devtools/platform/nsJSInspector.cpp b/devtools/platform/nsJSInspector.cpp
index aa74a1ed3d64..02822fb568a3 100644
--- a/devtools/platform/nsJSInspector.cpp
+++ b/devtools/platform/nsJSInspector.cpp
@@ -4,9 +4,9 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsJSInspector.h"
-#include "nsThreadUtils.h"
 #include "jsfriendapi.h"
 #include "mozilla/HoldDropJSObjects.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/dom/ScriptSettings.h"
 #include "nsServiceManagerUtils.h"
 #include "nsMemory.h"
diff --git a/dom/base/nsGlobalWindowInner.cpp b/dom/base/nsGlobalWindowInner.cpp
index 89708638e38b..48ae9b65f897 100644
--- a/dom/base/nsGlobalWindowInner.cpp
+++ b/dom/base/nsGlobalWindowInner.cpp
@@ -92,6 +92,7 @@
 #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"
diff --git a/dom/base/nsGlobalWindowOuter.cpp b/dom/base/nsGlobalWindowOuter.cpp
index b3f6ac1a921d..ba2bd841eb18 100644
--- a/dom/base/nsGlobalWindowOuter.cpp
+++ b/dom/base/nsGlobalWindowOuter.cpp
@@ -88,6 +88,7 @@
 #include "mozilla/dom/ScriptSettings.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Likely.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Sprintf.h"
 #include "mozilla/Unused.h"
 
diff --git a/dom/cache/Manager.cpp b/dom/cache/Manager.cpp
index 07e0558760a5..04e18d095ee3 100644
--- a/dom/cache/Manager.cpp
+++ b/dom/cache/Manager.cpp
@@ -8,6 +8,7 @@
 
 #include "mozilla/AutoRestore.h"
 #include "mozilla/Mutex.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticMutex.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/Unused.h"
diff --git a/dom/filehandle/ActorsParent.cpp b/dom/filehandle/ActorsParent.cpp
index 7d72b05e94e4..f104d694bbaf 100644
--- a/dom/filehandle/ActorsParent.cpp
+++ b/dom/filehandle/ActorsParent.cpp
@@ -9,6 +9,7 @@
 #include "mozilla/Assertions.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Unused.h"
 #include "mozilla/dom/BlobImpl.h"
 #include "mozilla/dom/File.h"
diff --git a/dom/indexedDB/ActorsParent.cpp b/dom/indexedDB/ActorsParent.cpp
index 0a06e613317d..596df7176d5a 100644
--- a/dom/indexedDB/ActorsParent.cpp
+++ b/dom/indexedDB/ActorsParent.cpp
@@ -84,6 +84,7 @@
 #include "mozilla/SchedulerGroup.h"
 #include "mozilla/Scoped.h"
 #include "mozilla/SnappyCompressOutputStream.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/TaskCategory.h"
 #include "mozilla/TimeStamp.h"
diff --git a/dom/ipc/ContentChild.cpp b/dom/ipc/ContentChild.cpp
index 5e0cfbffe7aa..642622b403e3 100644
--- a/dom/ipc/ContentChild.cpp
+++ b/dom/ipc/ContentChild.cpp
@@ -39,6 +39,7 @@
 #include "mozilla/RemoteLazyInputStreamChild.h"
 #include "mozilla/SchedulerGroup.h"
 #include "mozilla/SharedStyleSheetCache.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_fission.h"
 #include "mozilla/StaticPrefs_media.h"
diff --git a/dom/localstorage/ActorsParent.cpp b/dom/localstorage/ActorsParent.cpp
index 48b12ed6ff5d..2edab092ab67 100644
--- a/dom/localstorage/ActorsParent.cpp
+++ b/dom/localstorage/ActorsParent.cpp
@@ -46,6 +46,7 @@
 #include "mozilla/ResultExtensions.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/StoragePrincipalHelper.h"
diff --git a/dom/localstorage/LSObject.cpp b/dom/localstorage/LSObject.cpp
index bb680d0958d3..ca019e5bb249 100644
--- a/dom/localstorage/LSObject.cpp
+++ b/dom/localstorage/LSObject.cpp
@@ -21,6 +21,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/RemoteLazyInputStreamThread.h"
 #include "mozilla/ScopeExit.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticMutex.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StorageAccess.h"
diff --git a/dom/media/fuzz/FuzzMedia.cpp b/dom/media/fuzz/FuzzMedia.cpp
index f23abd6cfc3e..36515f5810e9 100644
--- a/dom/media/fuzz/FuzzMedia.cpp
+++ b/dom/media/fuzz/FuzzMedia.cpp
@@ -9,6 +9,7 @@
 #include "FlacDemuxer.h"
 #include "FuzzingInterface.h"
 #include "mozilla/AbstractThread.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "MP3Demuxer.h"
 #include "MP4Demuxer.h"
 #include "OggDemuxer.h"
diff --git a/dom/media/gmp/GMPServiceParent.cpp b/dom/media/gmp/GMPServiceParent.cpp
index def1260f2d2a..0c056b246a55 100644
--- a/dom/media/gmp/GMPServiceParent.cpp
+++ b/dom/media/gmp/GMPServiceParent.cpp
@@ -24,6 +24,7 @@
 #endif
 #include "VideoUtils.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_media.h"
 #include "mozilla/SyncRunnable.h"
 #include "mozilla/Unused.h"
diff --git a/dom/media/gtest/GMPTestMonitor.h b/dom/media/gtest/GMPTestMonitor.h
index ecd2d052d836..ae04ee83dd61 100644
--- a/dom/media/gtest/GMPTestMonitor.h
+++ b/dom/media/gtest/GMPTestMonitor.h
@@ -8,6 +8,7 @@
 
 #include "nsThreadUtils.h"
 #include "mozilla/SchedulerGroup.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 class GMPTestMonitor {
  public:
diff --git a/dom/media/gtest/TestAudioTrackGraph.cpp b/dom/media/gtest/TestAudioTrackGraph.cpp
index e231e14aeeb0..6cfb1b2cde7e 100644
--- a/dom/media/gtest/TestAudioTrackGraph.cpp
+++ b/dom/media/gtest/TestAudioTrackGraph.cpp
@@ -15,6 +15,7 @@
 #endif  // MOZ_WEBRTC
 #include "MockCubeb.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 #define DRIFT_BUFFERING_PREF "media.clockdrift.buffering"
 
diff --git a/dom/media/gtest/TestCDMStorage.cpp b/dom/media/gtest/TestCDMStorage.cpp
index 747a92d7fdfb..09f87fe07a96 100644
--- a/dom/media/gtest/TestCDMStorage.cpp
+++ b/dom/media/gtest/TestCDMStorage.cpp
@@ -12,6 +12,7 @@
 #include "gtest/gtest.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/SchedulerGroup.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsIFile.h"
 #include "nsNSSComponent.h"  //For EnsureNSSInitializedChromeOrContent
 #include "nsThreadUtils.h"
diff --git a/dom/media/gtest/TestDriftCompensation.cpp b/dom/media/gtest/TestDriftCompensation.cpp
index b03c6aa0532f..456da306401e 100644
--- a/dom/media/gtest/TestDriftCompensation.cpp
+++ b/dom/media/gtest/TestDriftCompensation.cpp
@@ -6,6 +6,7 @@
 
 #include "gtest/gtest.h"
 #include "DriftCompensation.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 using namespace mozilla;
 
diff --git a/dom/media/gtest/TestMediaDataDecoder.cpp b/dom/media/gtest/TestMediaDataDecoder.cpp
index f95adeefb738..f25ad048ee7f 100644
--- a/dom/media/gtest/TestMediaDataDecoder.cpp
+++ b/dom/media/gtest/TestMediaDataDecoder.cpp
@@ -12,6 +12,7 @@
 #include "WebMDecoder.h"
 #include "WebMDemuxer.h"
 #include "mozilla/AbstractThread.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsMimeTypes.h"
 
 using namespace mozilla;
diff --git a/dom/media/gtest/TestMediaDataEncoder.cpp b/dom/media/gtest/TestMediaDataEncoder.cpp
index b94f61b98612..6adeb73f3de2 100644
--- a/dom/media/gtest/TestMediaDataEncoder.cpp
+++ b/dom/media/gtest/TestMediaDataEncoder.cpp
@@ -8,6 +8,7 @@
 #include "AnnexB.h"
 #include "ImageContainer.h"
 #include "mozilla/AbstractThread.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/media/MediaUtils.h"  // For media::Await
 #include "nsMimeTypes.h"
 #include "PEMFactory.h"
diff --git a/dom/plugins/base/nsPluginHost.cpp b/dom/plugins/base/nsPluginHost.cpp
index 2910a25c3fa4..c74bb07b022f 100644
--- a/dom/plugins/base/nsPluginHost.cpp
+++ b/dom/plugins/base/nsPluginHost.cpp
@@ -48,6 +48,7 @@
 #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/ipc/URIUtils.h"
diff --git a/dom/quota/ActorsParent.cpp b/dom/quota/ActorsParent.cpp
index f2d0b9cb58d9..b216a099428c 100644
--- a/dom/quota/ActorsParent.cpp
+++ b/dom/quota/ActorsParent.cpp
@@ -55,6 +55,7 @@
 #include "mozilla/ResultExtensions.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/Telemetry.h"
diff --git a/dom/simpledb/ActorsParent.cpp b/dom/simpledb/ActorsParent.cpp
index be31beb3c686..6bca477f1210 100644
--- a/dom/simpledb/ActorsParent.cpp
+++ b/dom/simpledb/ActorsParent.cpp
@@ -25,6 +25,7 @@
 #include "mozilla/RefPtr.h"
 #include "mozilla/Result.h"
 #include "mozilla/ResultExtensions.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/Unused.h"
 #include "mozilla/Variant.h"
diff --git a/dom/storage/StorageObserver.cpp b/dom/storage/StorageObserver.cpp
index 54a230bfe42a..e8eed3c4efd5 100644
--- a/dom/storage/StorageObserver.cpp
+++ b/dom/storage/StorageObserver.cpp
@@ -25,6 +25,7 @@
 #include "mozilla/dom/LocalStorageCommon.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsServiceManagerUtils.h"
 
 namespace mozilla {
diff --git a/dom/xhr/XMLHttpRequestMainThread.cpp b/dom/xhr/XMLHttpRequestMainThread.cpp
index d54f6c39fa0f..bc7bb3af2b1a 100644
--- a/dom/xhr/XMLHttpRequestMainThread.cpp
+++ b/dom/xhr/XMLHttpRequestMainThread.cpp
@@ -36,6 +36,7 @@
 #include "mozilla/LoadInfo.h"
 #include "mozilla/LoadContext.h"
 #include "mozilla/MemoryReporting.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_network.h"
 #include "mozilla/StaticPrefs_privacy.h"
diff --git a/extensions/pref/autoconfig/src/nsAutoConfig.cpp b/extensions/pref/autoconfig/src/nsAutoConfig.cpp
index 3495da36d5ba..d841512c93d9 100644
--- a/extensions/pref/autoconfig/src/nsAutoConfig.cpp
+++ b/extensions/pref/autoconfig/src/nsAutoConfig.cpp
@@ -28,6 +28,7 @@
 
 #include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/Logging.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 using mozilla::LogLevel;
 
diff --git a/gfx/layers/ipc/CompositorBridgeChild.cpp b/gfx/layers/ipc/CompositorBridgeChild.cpp
index 572837253a66..48d7819ab477 100644
--- a/gfx/layers/ipc/CompositorBridgeChild.cpp
+++ b/gfx/layers/ipc/CompositorBridgeChild.cpp
@@ -42,6 +42,7 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/Unused.h"
 #include "mozilla/DebugOnly.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsThreadUtils.h"
 #if defined(XP_WIN)
 #  include "WinUtils.h"
diff --git a/gfx/layers/ipc/CompositorThread.cpp b/gfx/layers/ipc/CompositorThread.cpp
index 4835af3a0062..53a23cbc6f3a 100644
--- a/gfx/layers/ipc/CompositorThread.cpp
+++ b/gfx/layers/ipc/CompositorThread.cpp
@@ -9,6 +9,7 @@
 #include "MainThreadUtils.h"
 #include "VRManagerParent.h"
 #include "mozilla/BackgroundHangMonitor.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/layers/CanvasTranslator.h"
 #include "mozilla/layers/CompositorManagerParent.h"
 #include "mozilla/layers/ImageBridgeParent.h"
diff --git a/ipc/glue/BackgroundImpl.cpp b/ipc/glue/BackgroundImpl.cpp
index a68f2c79c3b2..4a2e88c75601 100644
--- a/ipc/glue/BackgroundImpl.cpp
+++ b/ipc/glue/BackgroundImpl.cpp
@@ -20,6 +20,7 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/MozPromise.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/Unused.h"
 #include "mozilla/dom/ContentChild.h"
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 20c4f244dffa..a7d984fabcc4 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -47,6 +47,7 @@
 #include "mozilla/Encoding.h"
 #include "mozilla/ErrorResult.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/WeakPtr.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_javascript.h"
diff --git a/layout/printing/ipc/RemotePrintJobChild.cpp b/layout/printing/ipc/RemotePrintJobChild.cpp
index ba49bd4fdacc..a7b7f5cfaa10 100644
--- a/layout/printing/ipc/RemotePrintJobChild.cpp
+++ b/layout/printing/ipc/RemotePrintJobChild.cpp
@@ -6,6 +6,7 @@
 
 #include "RemotePrintJobChild.h"
 
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Unused.h"
 #include "nsPagePrintTimer.h"
 #include "nsPrintJob.h"
diff --git a/media/webrtc/signaling/gtest/mediapipeline_unittest.cpp b/media/webrtc/signaling/gtest/mediapipeline_unittest.cpp
index 791680a35f8b..ba3a93b683fb 100644
--- a/media/webrtc/signaling/gtest/mediapipeline_unittest.cpp
+++ b/media/webrtc/signaling/gtest/mediapipeline_unittest.cpp
@@ -13,6 +13,7 @@
 #include "AudioStreamTrack.h"
 #include "mozilla/Mutex.h"
 #include "mozilla/RefPtr.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "MediaPipeline.h"
 #include "MediaPipelineFilter.h"
 #include "MediaTrackGraph.h"
diff --git a/modules/libpref/Preferences.cpp b/modules/libpref/Preferences.cpp
index 082f9a83a766..9f55be419eb8 100644
--- a/modules/libpref/Preferences.cpp
+++ b/modules/libpref/Preferences.cpp
@@ -33,6 +33,7 @@
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Services.h"
 #include "mozilla/ServoStyleSet.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticMutex.h"
 #include "mozilla/StaticPrefsAll.h"
 #include "mozilla/SyncRunnable.h"
diff --git a/netwerk/base/ProxyAutoConfig.cpp b/netwerk/base/ProxyAutoConfig.cpp
index a89840ad3d65..6635d89de822 100644
--- a/netwerk/base/ProxyAutoConfig.cpp
+++ b/netwerk/base/ProxyAutoConfig.cpp
@@ -24,6 +24,7 @@
 #include "prnetdb.h"
 #include "nsITimer.h"
 #include "mozilla/Atomics.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/net/DNS.h"
 #include "mozilla/Utf8.h"  // mozilla::Utf8Unit
 #include "nsServiceManagerUtils.h"
diff --git a/netwerk/base/nsAsyncRedirectVerifyHelper.cpp b/netwerk/base/nsAsyncRedirectVerifyHelper.cpp
index 40e98b4c50c2..d61c00414ce3 100644
--- a/netwerk/base/nsAsyncRedirectVerifyHelper.cpp
+++ b/netwerk/base/nsAsyncRedirectVerifyHelper.cpp
@@ -4,6 +4,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "mozilla/Logging.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsAsyncRedirectVerifyHelper.h"
 #include "nsThreadUtils.h"
 #include "nsNetUtil.h"
diff --git a/netwerk/base/nsSyncStreamListener.cpp b/netwerk/base/nsSyncStreamListener.cpp
index 6dfc3a0b386b..9bfcd63d6743 100644
--- a/netwerk/base/nsSyncStreamListener.cpp
+++ b/netwerk/base/nsSyncStreamListener.cpp
@@ -2,6 +2,7 @@
  * 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 "mozilla/SpinEventLoopUntil.h"
 #include "nsIOService.h"
 #include "nsSyncStreamListener.h"
 #include "nsThreadUtils.h"
diff --git a/netwerk/protocol/http/nsHttpConnectionMgr.cpp b/netwerk/protocol/http/nsHttpConnectionMgr.cpp
index b9f64caa5056..cad55e90a6a8 100644
--- a/netwerk/protocol/http/nsHttpConnectionMgr.cpp
+++ b/netwerk/protocol/http/nsHttpConnectionMgr.cpp
@@ -17,6 +17,7 @@
 
 #include "NullHttpTransaction.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Telemetry.h"
 #include "mozilla/Unused.h"
 #include "mozilla/net/DNS.h"
diff --git a/netwerk/test/fuzz/FuzzingStreamListener.h b/netwerk/test/fuzz/FuzzingStreamListener.h
index 9ec01a95c21b..97234bc7bafa 100644
--- a/netwerk/test/fuzz/FuzzingStreamListener.h
+++ b/netwerk/test/fuzz/FuzzingStreamListener.h
@@ -1,12 +1,12 @@
 #ifndef FuzzingStreamListener_h__
 #define FuzzingStreamListener_h__
 
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsCOMPtr.h"
 #include "nsNetCID.h"
 #include "nsString.h"
 #include "nsNetUtil.h"
 #include "nsIStreamListener.h"
-#include "nsThreadUtils.h"
 
 namespace mozilla {
 namespace net {
diff --git a/netwerk/test/fuzz/TestFtpFuzzing.cpp b/netwerk/test/fuzz/TestFtpFuzzing.cpp
index ef918eff0e55..9fde50427944 100644
--- a/netwerk/test/fuzz/TestFtpFuzzing.cpp
+++ b/netwerk/test/fuzz/TestFtpFuzzing.cpp
@@ -1,4 +1,5 @@
 #include "mozilla/Preferences.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 #include "nsCOMPtr.h"
 #include "nsNetCID.h"
diff --git a/netwerk/test/fuzz/TestHttpFuzzing.cpp b/netwerk/test/fuzz/TestHttpFuzzing.cpp
index b21b3ff7aa9e..5aabd903d84c 100644
--- a/netwerk/test/fuzz/TestHttpFuzzing.cpp
+++ b/netwerk/test/fuzz/TestHttpFuzzing.cpp
@@ -1,5 +1,6 @@
 #include "mozilla/LoadInfo.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 #include "nsCOMPtr.h"
 #include "nsNetCID.h"
diff --git a/netwerk/test/fuzz/TestWebsocketFuzzing.cpp b/netwerk/test/fuzz/TestWebsocketFuzzing.cpp
index 762b38025782..ce3668d680e9 100644
--- a/netwerk/test/fuzz/TestWebsocketFuzzing.cpp
+++ b/netwerk/test/fuzz/TestWebsocketFuzzing.cpp
@@ -2,6 +2,7 @@
 
 #include "FuzzingInterface.h"
 #include "FuzzyLayer.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsComponentManagerUtils.h"
 #include "nsCOMPtr.h"
 #include "nsContentUtils.h"
diff --git a/netwerk/test/gtest/TestBufferedInputStream.cpp b/netwerk/test/gtest/TestBufferedInputStream.cpp
index b405f44c48e4..09527318c591 100644
--- a/netwerk/test/gtest/TestBufferedInputStream.cpp
+++ b/netwerk/test/gtest/TestBufferedInputStream.cpp
@@ -1,5 +1,6 @@
 #include "gtest/gtest.h"
 
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsBufferedStreams.h"
 #include "nsStreamUtils.h"
 #include "nsIThread.h"
diff --git a/netwerk/test/gtest/TestCommon.h b/netwerk/test/gtest/TestCommon.h
index a0d4d9a567c0..67ff55b1fbc5 100644
--- a/netwerk/test/gtest/TestCommon.h
+++ b/netwerk/test/gtest/TestCommon.h
@@ -8,6 +8,7 @@
 #include <stdlib.h>
 #include "nsThreadUtils.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 //-----------------------------------------------------------------------------
 
diff --git a/netwerk/test/gtest/TestMIMEInputStream.cpp b/netwerk/test/gtest/TestMIMEInputStream.cpp
index a90d4d28aa38..ce7f5bd47d1f 100644
--- a/netwerk/test/gtest/TestMIMEInputStream.cpp
+++ b/netwerk/test/gtest/TestMIMEInputStream.cpp
@@ -1,6 +1,7 @@
 #include "gtest/gtest.h"
 
 #include "Helpers.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsComponentManagerUtils.h"
 #include "nsCOMPtr.h"
 #include "nsStreamUtils.h"
diff --git a/netwerk/test/gtest/TestPartiallySeekableInputStream.cpp b/netwerk/test/gtest/TestPartiallySeekableInputStream.cpp
index 306e01c5b5bf..1dffd6fcafe0 100644
--- a/netwerk/test/gtest/TestPartiallySeekableInputStream.cpp
+++ b/netwerk/test/gtest/TestPartiallySeekableInputStream.cpp
@@ -5,6 +5,7 @@
 #include "nsStreamUtils.h"
 #include "nsString.h"
 #include "nsStringStream.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/net/PartiallySeekableInputStream.h"
 
 using mozilla::GetCurrentSerialEventTarget;
diff --git a/storage/mozStorageConnection.cpp b/storage/mozStorageConnection.cpp
index 13c44e97aa37..3cbc5f629091 100644
--- a/storage/mozStorageConnection.cpp
+++ b/storage/mozStorageConnection.cpp
@@ -19,6 +19,7 @@
 #include "mozilla/Unused.h"
 #include "mozilla/dom/quota/QuotaObject.h"
 #include "mozilla/ScopeExit.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_storage.h"
 
 #include "mozIStorageCompletionCallback.h"
diff --git a/storage/mozStorageService.cpp b/storage/mozStorageService.cpp
index 0669ae77ed1f..57a87dec0dce 100644
--- a/storage/mozStorageService.cpp
+++ b/storage/mozStorageService.cpp
@@ -6,6 +6,7 @@
 
 #include "mozilla/Attributes.h"
 #include "mozilla/DebugOnly.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 #include "mozStorageService.h"
 #include "mozStorageConnection.h"
diff --git a/toolkit/components/places/Database.cpp b/toolkit/components/places/Database.cpp
index 906510033e30..fbd616a7720d 100644
--- a/toolkit/components/places/Database.cpp
+++ b/toolkit/components/places/Database.cpp
@@ -6,6 +6,7 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/DebugOnly.h"
 #include "mozilla/ScopeExit.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/JSONWriter.h"
 
 #include "Database.h"
diff --git a/toolkit/components/places/tests/gtest/places_test_harness.h b/toolkit/components/places/tests/gtest/places_test_harness.h
index a25be1e0a289..f6531fb7b32f 100644
--- a/toolkit/components/places/tests/gtest/places_test_harness.h
+++ b/toolkit/components/places/tests/gtest/places_test_harness.h
@@ -16,6 +16,7 @@
 #include "nsIThread.h"
 #include "nsIURI.h"
 #include "mozilla/IHistory.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozIStorageConnection.h"
 #include "mozIStorageStatement.h"
 #include "mozIStorageAsyncStatement.h"
diff --git a/toolkit/components/places/tests/gtest/test_IHistory.cpp b/toolkit/components/places/tests/gtest/test_IHistory.cpp
index 1f518f584831..e7123cdb6102 100644
--- a/toolkit/components/places/tests/gtest/test_IHistory.cpp
+++ b/toolkit/components/places/tests/gtest/test_IHistory.cpp
@@ -9,6 +9,7 @@
 #include "nsIPrefService.h"
 #include "nsString.h"
 #include "mozilla/Attributes.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_layout.h"
 #include "nsNetUtil.h"
 
diff --git a/toolkit/components/printingui/ipc/nsPrintingProxy.cpp b/toolkit/components/printingui/ipc/nsPrintingProxy.cpp
index 6a3578d64511..bad829b56220 100644
--- a/toolkit/components/printingui/ipc/nsPrintingProxy.cpp
+++ b/toolkit/components/printingui/ipc/nsPrintingProxy.cpp
@@ -10,6 +10,7 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/BrowserChild.h"
 #include "mozilla/layout/RemotePrintJobChild.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Unused.h"
 #include "nsIDocShell.h"
 #include "nsIPrintingPromptService.h"
diff --git a/toolkit/components/url-classifier/tests/gtest/Common.cpp b/toolkit/components/url-classifier/tests/gtest/Common.cpp
index 78f5919653d0..3a46d476a672 100644
--- a/toolkit/components/url-classifier/tests/gtest/Common.cpp
+++ b/toolkit/components/url-classifier/tests/gtest/Common.cpp
@@ -9,6 +9,7 @@
 #include "HashStore.h"
 #include "LookupCacheV4.h"
 #include "mozilla/Components.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Unused.h"
 #include "nsAppDirectoryServiceDefs.h"
 #include "nsIThread.h"
diff --git a/toolkit/xre/ProfileReset.cpp b/toolkit/xre/ProfileReset.cpp
index 80ea7bdf4938..f181e347886c 100644
--- a/toolkit/xre/ProfileReset.cpp
+++ b/toolkit/xre/ProfileReset.cpp
@@ -20,6 +20,7 @@
 #include "mozilla/XREAppData.h"
 
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Unused.h"
 #include "prtime.h"
 
diff --git a/uriloader/preload/gtest/TestFetchPreloader.cpp b/uriloader/preload/gtest/TestFetchPreloader.cpp
index 1531ef471a7c..4d4d2b5103ce 100644
--- a/uriloader/preload/gtest/TestFetchPreloader.cpp
+++ b/uriloader/preload/gtest/TestFetchPreloader.cpp
@@ -6,6 +6,7 @@
 #include "mozilla/FetchPreloader.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/PreloadHashKey.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsNetUtil.h"
 #include "nsIChannel.h"
 #include "nsIStreamListener.h"
diff --git a/widget/windows/nsDataObj.cpp b/widget/windows/nsDataObj.cpp
index b267608b4ec8..5fb55247960a 100644
--- a/widget/windows/nsDataObj.cpp
+++ b/widget/windows/nsDataObj.cpp
@@ -25,6 +25,7 @@
 #include "nsIURL.h"
 #include "nsNetUtil.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/Unused.h"
 #include "nsIOutputStream.h"
 #include "nscore.h"
diff --git a/xpcom/base/AppShutdown.cpp b/xpcom/base/AppShutdown.cpp
index c53eda4f6285..130027084c5a 100644
--- a/xpcom/base/AppShutdown.cpp
+++ b/xpcom/base/AppShutdown.cpp
@@ -17,6 +17,7 @@
 #include "mozilla/PoisonIOInterposer.h"
 #include "mozilla/Printf.h"
 #include "mozilla/scache/StartupCache.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StartupTimeline.h"
 #include "mozilla/StaticPrefs_toolkit.h"
 #include "mozilla/LateWriteChecks.h"
diff --git a/xpcom/tests/gtest/TestEventPriorities.cpp b/xpcom/tests/gtest/TestEventPriorities.cpp
index 00922f80eed7..dfe222ce01c4 100644
--- a/xpcom/tests/gtest/TestEventPriorities.cpp
+++ b/xpcom/tests/gtest/TestEventPriorities.cpp
@@ -9,6 +9,7 @@
 #include "nsXPCOM.h"
 #include "nsThreadUtils.h"
 #include "gtest/gtest.h"
+#include "mozilla/SpinEventLoopUntil.h"
 
 #include <functional>
 
diff --git a/xpcom/tests/gtest/TestInputStreamLengthHelper.cpp b/xpcom/tests/gtest/TestInputStreamLengthHelper.cpp
index b9fff721007d..2ae008c2c720 100644
--- a/xpcom/tests/gtest/TestInputStreamLengthHelper.cpp
+++ b/xpcom/tests/gtest/TestInputStreamLengthHelper.cpp
@@ -1,6 +1,7 @@
 #include "gtest/gtest.h"
 
 #include "mozilla/InputStreamLengthHelper.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsCOMPtr.h"
 #include "nsIInputStream.h"
 #include "nsStreamUtils.h"
diff --git a/xpcom/tests/gtest/TestMultiplexInputStream.cpp b/xpcom/tests/gtest/TestMultiplexInputStream.cpp
index 61174d4391b3..b607208a8db7 100644
--- a/xpcom/tests/gtest/TestMultiplexInputStream.cpp
+++ b/xpcom/tests/gtest/TestMultiplexInputStream.cpp
@@ -5,6 +5,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "gtest/gtest.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsIAsyncInputStream.h"
 #include "nsComponentManagerUtils.h"
 #include "nsIInputStream.h"
diff --git a/xpcom/tests/gtest/TestNonBlockingAsyncInputStream.cpp b/xpcom/tests/gtest/TestNonBlockingAsyncInputStream.cpp
index 29c2556a54a4..a961d8c14f80 100644
--- a/xpcom/tests/gtest/TestNonBlockingAsyncInputStream.cpp
+++ b/xpcom/tests/gtest/TestNonBlockingAsyncInputStream.cpp
@@ -1,6 +1,7 @@
 #include "gtest/gtest.h"
 
 #include "mozilla/NonBlockingAsyncInputStream.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsIAsyncInputStream.h"
 #include "nsStreamUtils.h"
 #include "nsString.h"
diff --git a/xpcom/tests/gtest/TestSlicedInputStream.cpp b/xpcom/tests/gtest/TestSlicedInputStream.cpp
index b5c32f4e8888..269e7f1e2f31 100644
--- a/xpcom/tests/gtest/TestSlicedInputStream.cpp
+++ b/xpcom/tests/gtest/TestSlicedInputStream.cpp
@@ -1,6 +1,7 @@
 #include "gtest/gtest.h"
 
 #include "mozilla/SlicedInputStream.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsCOMPtr.h"
 #include "nsIInputStream.h"
 #include "nsIPipe.h"
diff --git a/xpcom/tests/gtest/TestThreadUtils.cpp b/xpcom/tests/gtest/TestThreadUtils.cpp
index 34af41695f95..897f43e17dc7 100644
--- a/xpcom/tests/gtest/TestThreadUtils.cpp
+++ b/xpcom/tests/gtest/TestThreadUtils.cpp
@@ -8,6 +8,7 @@
 #include "nsThreadUtils.h"
 #include "mozilla/IdleTaskRunner.h"
 #include "mozilla/RefCounted.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/UniquePtr.h"
 
 #include "gtest/gtest.h"
diff --git a/xpcom/threads/SharedThreadPool.cpp b/xpcom/threads/SharedThreadPool.cpp
index 5f77a64e010c..fede9a2f394b 100644
--- a/xpcom/threads/SharedThreadPool.cpp
+++ b/xpcom/threads/SharedThreadPool.cpp
@@ -8,6 +8,7 @@
 #include "mozilla/Monitor.h"
 #include "mozilla/ReentrantMonitor.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPtr.h"
 #include "nsDataHashtable.h"
 #include "nsXPCOMCIDInternal.h"
diff --git a/xpcom/threads/SpinEventLoopUntil.h b/xpcom/threads/SpinEventLoopUntil.h
new file mode 100644
index 000000000000..398c7084a27f
--- /dev/null
+++ b/xpcom/threads/SpinEventLoopUntil.h
@@ -0,0 +1,108 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+#ifndef xpcom_threads_SpinEventLoopUntil_h__
+#define xpcom_threads_SpinEventLoopUntil_h__
+
+#include "MainThreadUtils.h"
+#include "mozilla/Maybe.h"
+#include "nsThreadUtils.h"
+#include "xpcpublic.h"
+
+class nsIThread;
+
+// A wrapper for nested event loops.
+//
+// This function is intended to make code more obvious (do you remember
+// what NS_ProcessNextEvent(nullptr, true) means?) and slightly more
+// efficient, as people often pass nullptr or NS_GetCurrentThread to
+// NS_ProcessNextEvent, which results in needless querying of the current
+// thread every time through the loop.
+//
+// You should use this function in preference to NS_ProcessNextEvent inside
+// a loop unless one of the following is true:
+//
+// * You need to pass `false` to NS_ProcessNextEvent; or
+// * You need to do unusual things around the call to NS_ProcessNextEvent,
+//   such as unlocking mutexes that you are holding.
+//
+// If you *do* need to call NS_ProcessNextEvent manually, please do call
+// NS_GetCurrentThread() outside of your loop and pass the returned pointer
+// into NS_ProcessNextEvent for a tiny efficiency win.
+namespace mozilla {
+
+// You should normally not need to deal with this template parameter.  If
+// you enjoy esoteric event loop details, read on.
+//
+// If you specify that NS_ProcessNextEvent wait for an event, it is possible
+// for NS_ProcessNextEvent to return false, i.e. to indicate that an event
+// was not processed.  This can only happen when the thread has been shut
+// down by another thread, but is still attempting to process events outside
+// of a nested event loop.
+//
+// This behavior is admittedly strange.  The scenario it deals with is the
+// following:
+//
+// * The current thread has been shut down by some owner thread.
+// * The current thread is spinning an event loop waiting for some condition
+//   to become true.
+// * Said condition is actually being fulfilled by another thread, so there
+//   are timing issues in play.
+//
+// Thus, there is a small window where the current thread's event loop
+// spinning can check the condition, find it false, and call
+// NS_ProcessNextEvent to wait for another event.  But we don't actually
+// want it to wait indefinitely, because there might not be any other events
+// in the event loop, and the current thread can't accept dispatched events
+// because it's being shut down.  Thus, actually blocking would hang the
+// thread, which is bad.  The solution, then, is to detect such a scenario
+// and not actually block inside NS_ProcessNextEvent.
+//
+// But this is a problem, because we want to return the status of
+// NS_ProcessNextEvent to the caller of SpinEventLoopUntil if possible.  In
+// the above scenario, however, we'd stop spinning prematurely and cause
+// all sorts of havoc.  We therefore have this template parameter to
+// control whether errors are ignored or passed out to the caller of
+// SpinEventLoopUntil.  The latter is the default; if you find yourself
+// wanting to use the former, you should think long and hard before doing
+// so, and write a comment like this defending your choice.
+
+enum class ProcessFailureBehavior {
+  IgnoreAndContinue,
+  ReportToCaller,
+};
+
+template <
+    ProcessFailureBehavior Behavior = ProcessFailureBehavior::ReportToCaller,
+    typename Pred>
+bool SpinEventLoopUntil(Pred&& aPredicate, nsIThread* aThread = nullptr) {
+  nsIThread* thread = aThread ? aThread : NS_GetCurrentThread();
+
+  // From a latency perspective, spinning the event loop is like leaving script
+  // and returning to the event loop. Tell the watchdog we stopped running
+  // script (until we return).
+  mozilla::Maybe<xpc::AutoScriptActivity> asa;
+  if (NS_IsMainThread()) {
+    asa.emplace(false);
+  }
+
+  while (!aPredicate()) {
+    bool didSomething = NS_ProcessNextEvent(thread, true);
+
+    if (Behavior == ProcessFailureBehavior::IgnoreAndContinue) {
+      // Don't care what happened, continue on.
+      continue;
+    } else if (!didSomething) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+}  // namespace mozilla
+
+#endif  // xpcom_threads_SpinEventLoopUntil_h__
diff --git a/xpcom/threads/ThreadEventTarget.cpp b/xpcom/threads/ThreadEventTarget.cpp
index c76986d82dfc..75a109cceb50 100644
--- a/xpcom/threads/ThreadEventTarget.cpp
+++ b/xpcom/threads/ThreadEventTarget.cpp
@@ -8,6 +8,7 @@
 #include "mozilla/ThreadEventQueue.h"
 
 #include "LeakRefPtr.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/TimeStamp.h"
 #include "nsComponentManagerUtils.h"
 #include "nsITimer.h"
diff --git a/xpcom/threads/moz.build b/xpcom/threads/moz.build
index e588d45284bd..0bd525e9e22b 100644
--- a/xpcom/threads/moz.build
+++ b/xpcom/threads/moz.build
@@ -64,6 +64,7 @@ EXPORTS.mozilla += [
     "RWLock.h",
     "SchedulerGroup.h",
     "SharedThreadPool.h",
+    "SpinEventLoopUntil.h",
     "StateMirroring.h",
     "StateWatching.h",
     "SynchronizedEventQueue.h",
diff --git a/xpcom/threads/nsThread.cpp b/xpcom/threads/nsThread.cpp
index 5c143579614e..8c27b8d3c0f2 100644
--- a/xpcom/threads/nsThread.cpp
+++ b/xpcom/threads/nsThread.cpp
@@ -31,6 +31,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/SchedulerGroup.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPrefs_threads.h"
 #include "mozilla/TaskController.h"
 #include "nsXPCOMPrivate.h"
diff --git a/xpcom/threads/nsThreadManager.cpp b/xpcom/threads/nsThreadManager.cpp
index c9fdf15b3234..7dfb54284290 100644
--- a/xpcom/threads/nsThreadManager.cpp
+++ b/xpcom/threads/nsThreadManager.cpp
@@ -17,6 +17,7 @@
 #include "mozilla/InputTaskManager.h"
 #include "mozilla/Mutex.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/StaticPtr.h"
 #include "mozilla/TaskQueue.h"
 #include "mozilla/ThreadEventQueue.h"
diff --git a/xpcom/threads/nsThreadPool.cpp b/xpcom/threads/nsThreadPool.cpp
index a60e498751de..32789240fdb6 100644
--- a/xpcom/threads/nsThreadPool.cpp
+++ b/xpcom/threads/nsThreadPool.cpp
@@ -13,6 +13,7 @@
 #include "prinrval.h"
 #include "mozilla/Logging.h"
 #include "mozilla/SchedulerGroup.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "nsThreadSyncDispatch.h"
 
 #include <mutex>
diff --git a/xpcom/threads/nsThreadUtils.h b/xpcom/threads/nsThreadUtils.h
index e1cd094d6271..f7c907ab38ae 100644
--- a/xpcom/threads/nsThreadUtils.h
+++ b/xpcom/threads/nsThreadUtils.h
@@ -25,15 +25,14 @@
 #include "nsIIdleRunnable.h"
 #include "nsINamed.h"
 #include "nsIRunnable.h"
-#include "nsIThread.h"
 #include "nsIThreadManager.h"
 #include "nsITimer.h"
 #include "nsString.h"
 #include "prinrval.h"
 #include "prthread.h"
-#include "xpcpublic.h"
 
 class MessageLoop;
+class nsIThread;
 
 //-----------------------------------------------------------------------------
 // These methods are alternatives to the methods on nsIThreadManager, provided
@@ -283,97 +282,6 @@ extern bool NS_HasPendingEvents(nsIThread* aThread = nullptr);
 extern bool NS_ProcessNextEvent(nsIThread* aThread = nullptr,
                                 bool aMayWait = true);
 
-// A wrapper for nested event loops.
-//
-// This function is intended to make code more obvious (do you remember
-// what NS_ProcessNextEvent(nullptr, true) means?) and slightly more
-// efficient, as people often pass nullptr or NS_GetCurrentThread to
-// NS_ProcessNextEvent, which results in needless querying of the current
-// thread every time through the loop.
-//
-// You should use this function in preference to NS_ProcessNextEvent inside
-// a loop unless one of the following is true:
-//
-// * You need to pass `false` to NS_ProcessNextEvent; or
-// * You need to do unusual things around the call to NS_ProcessNextEvent,
-//   such as unlocking mutexes that you are holding.
-//
-// If you *do* need to call NS_ProcessNextEvent manually, please do call
-// NS_GetCurrentThread() outside of your loop and pass the returned pointer
-// into NS_ProcessNextEvent for a tiny efficiency win.
-namespace mozilla {
-
-// You should normally not need to deal with this template parameter.  If
-// you enjoy esoteric event loop details, read on.
-//
-// If you specify that NS_ProcessNextEvent wait for an event, it is possible
-// for NS_ProcessNextEvent to return false, i.e. to indicate that an event
-// was not processed.  This can only happen when the thread has been shut
-// down by another thread, but is still attempting to process events outside
-// of a nested event loop.
-//
-// This behavior is admittedly strange.  The scenario it deals with is the
-// following:
-//
-// * The current thread has been shut down by some owner thread.
-// * The current thread is spinning an event loop waiting for some condition
-//   to become true.
-// * Said condition is actually being fulfilled by another thread, so there
-//   are timing issues in play.
-//
-// Thus, there is a small window where the current thread's event loop
-// spinning can check the condition, find it false, and call
-// NS_ProcessNextEvent to wait for another event.  But we don't actually
-// want it to wait indefinitely, because there might not be any other events
-// in the event loop, and the current thread can't accept dispatched events
-// because it's being shut down.  Thus, actually blocking would hang the
-// thread, which is bad.  The solution, then, is to detect such a scenario
-// and not actually block inside NS_ProcessNextEvent.
-//
-// But this is a problem, because we want to return the status of
-// NS_ProcessNextEvent to the caller of SpinEventLoopUntil if possible.  In
-// the above scenario, however, we'd stop spinning prematurely and cause
-// all sorts of havoc.  We therefore have this template parameter to
-// control whether errors are ignored or passed out to the caller of
-// SpinEventLoopUntil.  The latter is the default; if you find yourself
-// wanting to use the former, you should think long and hard before doing
-// so, and write a comment like this defending your choice.
-
-enum class ProcessFailureBehavior {
-  IgnoreAndContinue,
-  ReportToCaller,
-};
-
-template <
-    ProcessFailureBehavior Behavior = ProcessFailureBehavior::ReportToCaller,
-    typename Pred>
-bool SpinEventLoopUntil(Pred&& aPredicate, nsIThread* aThread = nullptr) {
-  nsIThread* thread = aThread ? aThread : NS_GetCurrentThread();
-
-  // From a latency perspective, spinning the event loop is like leaving script
-  // and returning to the event loop. Tell the watchdog we stopped running
-  // script (until we return).
-  mozilla::Maybe<xpc::AutoScriptActivity> asa;
-  if (NS_IsMainThread()) {
-    asa.emplace(false);
-  }
-
-  while (!aPredicate()) {
-    bool didSomething = NS_ProcessNextEvent(thread, true);
-
-    if (Behavior == ProcessFailureBehavior::IgnoreAndContinue) {
-      // Don't care what happened, continue on.
-      continue;
-    } else if (!didSomething) {
-      return false;
-    }
-  }
-
-  return true;
-}
-
-}  // namespace mozilla
-
 /**
  * Returns true if we're in the compositor thread.
  *
diff --git a/xpfe/appshell/AppWindow.cpp b/xpfe/appshell/AppWindow.cpp
index 8b361e2f84de..c6eeac6bb478 100644
--- a/xpfe/appshell/AppWindow.cpp
+++ b/xpfe/appshell/AppWindow.cpp
@@ -56,6 +56,7 @@
 #include "mozilla/Preferences.h"
 #include "mozilla/PresShell.h"
 #include "mozilla/Services.h"
+#include "mozilla/SpinEventLoopUntil.h"
 #include "mozilla/dom/BarProps.h"
 #include "mozilla/dom/DOMRect.h"
 #include "mozilla/dom/Element.h"