diff --git a/dom/svg/SVGGeometryElement.cpp b/dom/svg/SVGGeometryElement.cpp
index e5c57c3f771c..5f92563b4b33 100644
--- a/dom/svg/SVGGeometryElement.cpp
+++ b/dom/svg/SVGGeometryElement.cpp
@@ -19,6 +19,7 @@
 #include "mozilla/dom/SVGLengthBinding.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/RefPtr.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/SVGContentUtils.h"
 
 using namespace mozilla::gfx;
diff --git a/dom/svg/SVGPathElement.cpp b/dom/svg/SVGPathElement.cpp
index 81c333a6f3de..b3fb7af260dc 100644
--- a/dom/svg/SVGPathElement.cpp
+++ b/dom/svg/SVGPathElement.cpp
@@ -21,6 +21,7 @@
 #include "mozilla/dom/SVGPathElementBinding.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/RefPtr.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/SVGContentUtils.h"
 
 NS_IMPL_NS_NEW_SVG_ELEMENT(Path)
diff --git a/gfx/layers/wr/OMTAController.cpp b/gfx/layers/wr/OMTAController.cpp
index a928b2a15ae1..527ec881f6a6 100644
--- a/gfx/layers/wr/OMTAController.cpp
+++ b/gfx/layers/wr/OMTAController.cpp
@@ -8,6 +8,7 @@
 
 #include "mozilla/layers/CompositorBridgeParent.h"
 #include "mozilla/layers/CompositorThread.h"
+#include "mozilla/StaticPrefs_layout.h"
 
 namespace mozilla {
 namespace layers {
diff --git a/gfx/src/nsDeviceContext.cpp b/gfx/src/nsDeviceContext.cpp
index 97cc50c6d325..78ee8b034e35 100644
--- a/gfx/src/nsDeviceContext.cpp
+++ b/gfx/src/nsDeviceContext.cpp
@@ -15,13 +15,14 @@
 #include "mozilla/gfx/PrintTarget.h"
 #include "mozilla/Preferences.h"  // for Preferences
 #include "mozilla/Services.h"     // for GetObserverService
-#include "mozilla/mozalloc.h"     // for operator new
-#include "nsCRT.h"                // for nsCRT
-#include "nsDebug.h"              // for NS_ASSERTION, etc
-#include "nsFont.h"               // for nsFont
-#include "nsFontCache.h"          // for nsFontCache
-#include "nsFontMetrics.h"        // for nsFontMetrics
-#include "nsAtom.h"               // for nsAtom, NS_Atomize
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/mozalloc.h"  // for operator new
+#include "nsCRT.h"             // for nsCRT
+#include "nsDebug.h"           // for NS_ASSERTION, etc
+#include "nsFont.h"            // for nsFont
+#include "nsFontCache.h"       // for nsFontCache
+#include "nsFontMetrics.h"     // for nsFontMetrics
+#include "nsAtom.h"            // for nsAtom, NS_Atomize
 #include "nsID.h"
 #include "nsIDeviceContextSpec.h"   // for nsIDeviceContextSpec
 #include "nsLanguageAtomService.h"  // for nsLanguageAtomService
diff --git a/layout/generic/ScrollSnap.cpp b/layout/generic/ScrollSnap.cpp
index b400a62689fd..8efbaa00118a 100644
--- a/layout/generic/ScrollSnap.cpp
+++ b/layout/generic/ScrollSnap.cpp
@@ -14,6 +14,7 @@
 #include "nsLayoutUtils.h"
 #include "nsPresContext.h"
 #include "nsTArray.h"
+#include "mozilla/StaticPrefs_layout.h"
 
 namespace mozilla {
 
diff --git a/layout/generic/nsFlexContainerFrame.cpp b/layout/generic/nsFlexContainerFrame.cpp
index 400d33889212..3e14022f0ee2 100644
--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -16,6 +16,7 @@
 #include "mozilla/FloatingPoint.h"
 #include "mozilla/Logging.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/WritingModes.h"
 #include "nsBlockFrame.h"
 #include "nsContentUtils.h"
diff --git a/layout/painting/RetainedDisplayListBuilder.cpp b/layout/painting/RetainedDisplayListBuilder.cpp
index 5e4a7682db7b..a1cf61cd558b 100644
--- a/layout/painting/RetainedDisplayListBuilder.cpp
+++ b/layout/painting/RetainedDisplayListBuilder.cpp
@@ -71,6 +71,10 @@
 
 namespace mozilla {
 
+RetainedDisplayListData::RetainedDisplayListData()
+    : mModifiedFrameLimit(
+          StaticPrefs::layout_display_list_rebuild_frame_limit()) {}
+
 void RetainedDisplayListData::AddModifiedFrame(nsIFrame* aFrame) {
   MOZ_ASSERT(!aFrame->IsFrameModified());
   Flags(aFrame) += RetainedDisplayListData::FrameFlag::Modified;
diff --git a/layout/painting/RetainedDisplayListBuilder.h b/layout/painting/RetainedDisplayListBuilder.h
index 4cbd58d63571..1b22bfc06d55 100644
--- a/layout/painting/RetainedDisplayListBuilder.h
+++ b/layout/painting/RetainedDisplayListBuilder.h
@@ -26,10 +26,7 @@ struct RetainedDisplayListData {
   enum class FrameFlag : uint8_t { Modified, HasProps, HadWillChange };
   using FrameFlags = mozilla::EnumSet<FrameFlag, uint8_t>;
 
-  RetainedDisplayListData() : mModifiedFrameCount(0) {
-    mModifiedFrameLimit =
-        StaticPrefs::layout_display_list_rebuild_frame_limit();
-  }
+  RetainedDisplayListData();
 
   /**
    * Adds the frame to modified frames list.
@@ -86,8 +83,8 @@ struct RetainedDisplayListData {
 
  private:
   nsTHashMap<nsPtrHashKey<nsIFrame>, FrameFlags> mFrames;
-  uint32_t mModifiedFrameCount;
-  uint32_t mModifiedFrameLimit;
+  uint32_t mModifiedFrameCount = 0;
+  uint32_t mModifiedFrameLimit; // initialized to a pref value in constructor
 };
 
 enum class PartialUpdateResult { Failed, NoChange, Updated };
diff --git a/layout/style/nsCSSPseudoElements.h b/layout/style/nsCSSPseudoElements.h
index 244810943a1f..dcfdd9768bb9 100644
--- a/layout/style/nsCSSPseudoElements.h
+++ b/layout/style/nsCSSPseudoElements.h
@@ -13,7 +13,6 @@
 #include "mozilla/CSSEnabledState.h"
 #include "mozilla/Compiler.h"
 #include "mozilla/PseudoStyleType.h"
-#include "mozilla/StaticPrefs_layout.h"
 
 // Is this pseudo-element a CSS2 pseudo-element that can be specified
 // with the single colon syntax (in addition to the double-colon syntax,
diff --git a/layout/style/nsStyleStruct.cpp b/layout/style/nsStyleStruct.cpp
index 1dcfc3600b15..3e3b480babc8 100644
--- a/layout/style/nsStyleStruct.cpp
+++ b/layout/style/nsStyleStruct.cpp
@@ -3311,6 +3311,15 @@ nsChangeHint nsStyleUIReset::CalcDifference(
   return hint;
 }
 
+StyleScrollbarWidth nsStyleUIReset::ScrollbarWidth() const {
+  if (MOZ_UNLIKELY(StaticPrefs::layout_css_scrollbar_width_thin_disabled())) {
+    if (mScrollbarWidth == StyleScrollbarWidth::Thin) {
+      return StyleScrollbarWidth::Auto;
+    }
+  }
+  return mScrollbarWidth;
+}
+
 //-----------------------
 // nsStyleEffects
 //
diff --git a/layout/style/nsStyleStruct.h b/layout/style/nsStyleStruct.h
index 366ad1f281e6..a9f024e664f6 100644
--- a/layout/style/nsStyleStruct.h
+++ b/layout/style/nsStyleStruct.h
@@ -16,7 +16,6 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/ServoStyleConstsInlines.h"
-#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/UniquePtr.h"
 #include "nsColor.h"
 #include "nsCoord.h"
@@ -1795,15 +1794,7 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleUIReset {
  public:
   mozilla::StyleUserSelect ComputedUserSelect() const { return mUserSelect; }
 
-  mozilla::StyleScrollbarWidth ScrollbarWidth() const {
-    if (MOZ_UNLIKELY(
-            mozilla::StaticPrefs::layout_css_scrollbar_width_thin_disabled())) {
-      if (mScrollbarWidth == mozilla::StyleScrollbarWidth::Thin) {
-        return mozilla::StyleScrollbarWidth::Auto;
-      }
-    }
-    return mScrollbarWidth;
-  }
+  mozilla::StyleScrollbarWidth ScrollbarWidth() const;
 
   nsCSSPropertyID GetTransitionProperty(uint32_t aIndex) const {
     return mTransitions[aIndex % mTransitionPropertyCount].GetProperty();
diff --git a/layout/tables/nsTableCellFrame.cpp b/layout/tables/nsTableCellFrame.cpp
index e84598ecca92..375a847b31df 100644
--- a/layout/tables/nsTableCellFrame.cpp
+++ b/layout/tables/nsTableCellFrame.cpp
@@ -9,6 +9,7 @@
 #include "gfxUtils.h"
 #include "mozilla/ComputedStyle.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/Helpers.h"
 #include "nsTableFrame.h"
diff --git a/layout/tables/nsTableColFrame.cpp b/layout/tables/nsTableColFrame.cpp
index a289b1e269e9..92c98deba7c3 100644
--- a/layout/tables/nsTableColFrame.cpp
+++ b/layout/tables/nsTableColFrame.cpp
@@ -13,6 +13,7 @@
 #include "nsIContent.h"
 #include "mozilla/ComputedStyle.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_layout.h"
 
 using namespace mozilla;
 
diff --git a/layout/tables/nsTableRowFrame.cpp b/layout/tables/nsTableRowFrame.cpp
index 5a428ab486ac..b6e212efc5e9 100644
--- a/layout/tables/nsTableRowFrame.cpp
+++ b/layout/tables/nsTableRowFrame.cpp
@@ -10,6 +10,7 @@
 #include "nsTableRowGroupFrame.h"
 #include "nsPresContext.h"
 #include "mozilla/ComputedStyle.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "nsStyleConsts.h"
 #include "nsGkAtoms.h"
 #include "nsIContent.h"
diff --git a/layout/tables/nsTableRowGroupFrame.cpp b/layout/tables/nsTableRowGroupFrame.cpp
index 6252a7eb4d9b..df6872d35f50 100644
--- a/layout/tables/nsTableRowGroupFrame.cpp
+++ b/layout/tables/nsTableRowGroupFrame.cpp
@@ -6,6 +6,7 @@
 
 #include "mozilla/ComputedStyle.h"
 #include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_layout.h"
 
 #include "nsCOMPtr.h"
 #include "nsTableRowFrame.h"
diff --git a/widget/ThemeColors.cpp b/widget/ThemeColors.cpp
index aaddd550798f..ead5042229e7 100644
--- a/widget/ThemeColors.cpp
+++ b/widget/ThemeColors.cpp
@@ -6,6 +6,7 @@
 #include "ThemeColors.h"
 
 #include "mozilla/RelativeLuminanceUtils.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/StaticPrefs_widget.h"
 #include "ThemeDrawing.h"
 #include "nsNativeTheme.h"
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index 8d4f6e0d6072..2cc19b5fba72 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -54,6 +54,7 @@
 #include "mozilla/ProfilerLabels.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/StaticPrefs_apz.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/StaticPrefs_mozilla.h"
 #include "mozilla/StaticPrefs_ui.h"
 #include "mozilla/StaticPrefs_widget.h"
diff --git a/widget/nsXPLookAndFeel.cpp b/widget/nsXPLookAndFeel.cpp
index a74fdda891c7..1a635fa38071 100644
--- a/widget/nsXPLookAndFeel.cpp
+++ b/widget/nsXPLookAndFeel.cpp
@@ -26,6 +26,7 @@
 #include "mozilla/ServoCSSParser.h"
 #include "mozilla/StaticPrefs_browser.h"
 #include "mozilla/StaticPrefs_editor.h"
+#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/StaticPrefs_ui.h"
 #include "mozilla/StaticPrefs_widget.h"
 #include "mozilla/dom/Document.h"