diff --git a/widget/LookAndFeel.h b/widget/LookAndFeel.h
index 92c97fe0ae44..216c70fdb84d 100644
--- a/widget/LookAndFeel.h
+++ b/widget/LookAndFeel.h
@@ -534,6 +534,10 @@ class LookAndFeel {
    * or not.
    */
   static void SetShouldRetainCacheForTest(bool aValue);
+
+  static void SetPrefersReducedMotionOverrideForTest(bool aValue);
+
+  static void ResetPrefersReducedMotionOverrideForTest();
 };
 
 }  // namespace mozilla
diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 3a5e4252994a..30e3aa719952 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -2190,24 +2190,7 @@ void nsChildView::LookUpDictionary(const nsAString& aText,
 }
 
 nsresult nsChildView::SetPrefersReducedMotionOverrideForTest(bool aValue) {
-  // Tell that the cache value we are going to set isn't cleared via
-  // nsPresContext::ThemeChangedInternal which is called right before
-  // we queue the media feature value change for this prefers-reduced-motion
-  // change.
-  LookAndFeel::SetShouldRetainCacheForTest(true);
-
-  LookAndFeelInt prefersReducedMotion;
-  prefersReducedMotion.id = LookAndFeel::eIntID_PrefersReducedMotion;
-  prefersReducedMotion.value = aValue ? 1 : 0;
-
-  AutoTArray<LookAndFeelInt, 1> lookAndFeelCache;
-  lookAndFeelCache.AppendElement(prefersReducedMotion);
-
-  // If we could have a way to modify
-  // NSWorkspace.accessibilityDisplayShouldReduceMotion, we could use it, but
-  // unfortunately there is no way, so we change the cache value instead as if
-  // it's set in the parent process.
-  LookAndFeel::SetIntCache(lookAndFeelCache);
+  LookAndFeel::SetPrefersReducedMotionOverrideForTest(aValue);
 
   if (nsCocoaFeatures::OnMojaveOrLater() &&
       NSWorkspaceAccessibilityDisplayOptionsDidChangeNotification) {
@@ -2227,7 +2210,7 @@ nsresult nsChildView::SetPrefersReducedMotionOverrideForTest(bool aValue) {
 }
 
 nsresult nsChildView::ResetPrefersReducedMotionOverrideForTest() {
-  LookAndFeel::SetShouldRetainCacheForTest(false);
+  LookAndFeel::ResetPrefersReducedMotionOverrideForTest();
   return NS_OK;
 }
 
diff --git a/widget/cocoa/nsLookAndFeel.h b/widget/cocoa/nsLookAndFeel.h
index 6185c1d42934..718bc04b60da 100644
--- a/widget/cocoa/nsLookAndFeel.h
+++ b/widget/cocoa/nsLookAndFeel.h
@@ -45,9 +45,6 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   int32_t mAllowOverlayScrollbarsOverlap;
   bool mAllowOverlayScrollbarsOverlapCached;
 
-  int32_t mPrefersReducedMotion;
-  bool mPrefersReducedMotionCached;
-
   int32_t mSystemUsesDarkTheme;
   bool mSystemUsesDarkThemeCached;
 
diff --git a/widget/cocoa/nsLookAndFeel.mm b/widget/cocoa/nsLookAndFeel.mm
index 182b640ca4a9..fe6fabd2648c 100644
--- a/widget/cocoa/nsLookAndFeel.mm
+++ b/widget/cocoa/nsLookAndFeel.mm
@@ -40,8 +40,6 @@ nsLookAndFeel::nsLookAndFeel()
       mUseOverlayScrollbarsCached(false),
       mAllowOverlayScrollbarsOverlap(-1),
       mAllowOverlayScrollbarsOverlapCached(false),
-      mPrefersReducedMotion(-1),
-      mPrefersReducedMotionCached(false),
       mSystemUsesDarkTheme(-1),
       mSystemUsesDarkThemeCached(false),
       mColorTextSelectBackground(0),
diff --git a/widget/gtk/nsLookAndFeel.h b/widget/gtk/nsLookAndFeel.h
index 5f68c8e52e15..8c0bffcc5312 100644
--- a/widget/gtk/nsLookAndFeel.h
+++ b/widget/gtk/nsLookAndFeel.h
@@ -92,7 +92,6 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   char16_t mInvisibleCharacter = 0;
   float mCaretRatio = 0.0f;
   int32_t mCaretBlinkTime = 0;
-  int32_t mPrefersReducedMotion = -1;
   bool mMenuSupportsDrag = false;
   bool mCSDAvailable = false;
   bool mCSDHideTitlebarByDefault = false;
@@ -103,7 +102,6 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
   bool mSystemUsesDarkTheme = false;
   bool mHighContrast = false;
   bool mInitialized = false;
-  bool mPrefersReducedMotionCached = false;
 
   void EnsureInit();
   void ConfigureContentGtkTheme();
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index 82b346e0a45a..da21967cf20b 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -7722,16 +7722,7 @@ void nsWindow::LockAspectRatio(bool aShouldLock) {
 }
 
 nsresult nsWindow::SetPrefersReducedMotionOverrideForTest(bool aValue) {
-  LookAndFeel::SetShouldRetainCacheForTest(true);
-
-  LookAndFeelInt prefersReducedMotion;
-  prefersReducedMotion.id = LookAndFeel::eIntID_PrefersReducedMotion;
-  prefersReducedMotion.value = aValue ? 1 : 0;
-
-  AutoTArray<LookAndFeelInt, 1> lookAndFeelCache;
-  lookAndFeelCache.AppendElement(prefersReducedMotion);
-
-  LookAndFeel::SetIntCache(lookAndFeelCache);
+  LookAndFeel::SetPrefersReducedMotionOverrideForTest(aValue);
 
   // Notify as if the corresponding setting changed.
   g_object_notify(G_OBJECT(gtk_settings_get_default()),
@@ -7741,7 +7732,7 @@ nsresult nsWindow::SetPrefersReducedMotionOverrideForTest(bool aValue) {
 }
 
 nsresult nsWindow::ResetPrefersReducedMotionOverrideForTest() {
-  LookAndFeel::SetShouldRetainCacheForTest(false);
+  LookAndFeel::ResetPrefersReducedMotionOverrideForTest();
 
   return NS_OK;
 }
diff --git a/widget/nsXPLookAndFeel.cpp b/widget/nsXPLookAndFeel.cpp
index 8f771f6137f4..460c2dc629e1 100644
--- a/widget/nsXPLookAndFeel.cpp
+++ b/widget/nsXPLookAndFeel.cpp
@@ -258,9 +258,6 @@ void nsXPLookAndFeel::Shutdown() {
   sInstance = nullptr;
 }
 
-nsXPLookAndFeel::nsXPLookAndFeel()
-    : LookAndFeel(), mShouldRetainCacheForTest(false) {}
-
 // static
 void nsXPLookAndFeel::IntPrefChanged(nsLookAndFeelIntPref* data) {
   if (!data) {
@@ -1093,4 +1090,26 @@ void LookAndFeel::SetShouldRetainCacheForTest(bool aValue) {
   nsLookAndFeel::GetInstance()->SetShouldRetainCacheImplForTest(aValue);
 }
 
+// static
+void LookAndFeel::SetPrefersReducedMotionOverrideForTest(bool aValue) {
+  // Tell that the cache value we are going to set isn't cleared via
+  // nsPresContext::ThemeChangedInternal which is called right before
+  // we queue the media feature value change for this prefers-reduced-motion
+  // change.
+  SetShouldRetainCacheForTest(true);
+
+  int32_t value = aValue ? 1 : 0;
+
+  AutoTArray<LookAndFeelInt, 1> lookAndFeelCache;
+  lookAndFeelCache.AppendElement(
+      LookAndFeelInt{.id = eIntID_PrefersReducedMotion, {.value = value}});
+
+  SetIntCache(lookAndFeelCache);
+}
+
+// static
+void LookAndFeel::ResetPrefersReducedMotionOverrideForTest() {
+  SetShouldRetainCacheForTest(false);
+}
+
 }  // namespace mozilla
diff --git a/widget/nsXPLookAndFeel.h b/widget/nsXPLookAndFeel.h
index 2e0f9aff2266..5e31aa83ce63 100644
--- a/widget/nsXPLookAndFeel.h
+++ b/widget/nsXPLookAndFeel.h
@@ -91,7 +91,7 @@ class nsXPLookAndFeel : public mozilla::LookAndFeel {
   }
 
  protected:
-  nsXPLookAndFeel();
+  nsXPLookAndFeel() = default;
 
   static void IntPrefChanged(nsLookAndFeelIntPref* data);
   static void FloatPrefChanged(nsLookAndFeelFloatPref* data);
@@ -124,9 +124,11 @@ class nsXPLookAndFeel : public mozilla::LookAndFeel {
   static bool sIsInPrefersReducedMotionForTest;
   static bool sPrefersReducedMotionForTest;
 
+  int32_t mPrefersReducedMotion = -1;
+  bool mPrefersReducedMotionCached = false;
   // True if we shouldn't clear the cache value in RefreshImpl().
   // NOTE: This should be used only for testing.
-  bool mShouldRetainCacheForTest;
+  bool mShouldRetainCacheForTest = false;
 };
 
 #endif