browser(firefox): added reduced motion emulation (#6618)

2025-06-26 21:40:17 +00:00 · 2021-05-18 21:23:12 +02:00 · 2021-05-18 21:23:12 +02:00 · c4a6c2bcab
commit c4a6c2bcab
parent 36c0765c98
14 changed files with 522 additions and 30 deletions
--- a/browser_patches/firefox-stable/BUILD_NUMBER
+++ b/browser_patches/firefox-stable/BUILD_NUMBER
@ -1,2 +1,2 @@
-1253
-Changed: aslushnikov@gmail.com Fri 14 May 2021 21:37:19 PM PDT
+1254
+Changed: max@schmitt.mx Di 18. Mai 21:21:37 CEST 2021
--- a/browser_patches/firefox-stable/juggler/TargetRegistry.js
+++ b/browser_patches/firefox-stable/juggler/TargetRegistry.js
@ -159,6 +159,7 @@ class TargetRegistry {
      target.updateUserAgent();
      target.updateTouchOverride();
      target.updateColorSchemeOverride();
+      target.updateReducedMotionOverride();
      if (!hasExplicitSize)
        target.updateViewportSize();
      if (browserContext.videoRecordingOptions)
@ -437,6 +438,14 @@ class PageTarget {
    this._linkedBrowser.browsingContext.prefersColorSchemeOverride = this.colorScheme || this._browserContext.colorScheme || 'none';
  }

+  setReducedMotion(reducedMotion) {
+    this.reducedMotion = fromProtocolReducedMotion(reducedMotion);
+    this.updateReducedMotionOverride();
+  }
+
+  updateReducedMotionOverride() {
+    this._linkedBrowser.browsingContext.prefersReducedMotionOverride = this.reducedMotion || this._browserContext.reducedMotion || 'none';
+  }

  async setViewportSize(viewportSize) {
    this._viewportSize = viewportSize;
@ -612,6 +621,14 @@ function fromProtocolColorScheme(colorScheme) {
  throw new Error('Unknown color scheme: ' + colorScheme);
 }

+function fromProtocolReducedMotion(reducedMotion) {
+  if (reducedMotion === 'reduce')
+    return reducedMotion;
+  if (reducedMotion === null || reducedMotion === 'no-preference')
+    return undefined;
+  throw new Error('Unknown reduced motion: ' + reducedMotion);
+}
+
 class BrowserContext {
  constructor(registry, browserContextId, removeOnDetach) {
    this._registry = registry;
@ -639,6 +656,7 @@ class BrowserContext {
    this.defaultUserAgent = null;
    this.touchOverride = false;
    this.colorScheme = 'none';
+    this.reducedMotion = 'none';
    this.videoRecordingOptions = undefined;
    this.scriptsToEvaluateOnNewDocument = [];
    this.bindings = [];
@ -652,6 +670,12 @@ class BrowserContext {
      page.updateColorSchemeOverride();
  }

+  setReducedMotion(reducedMotion) {
+    this.reducedMotion = fromProtocolReducedMotion(reducedMotion);
+    for (const page of this.pages)
+      page.updateReducedMotionOverride();
+  }
+
  async destroy() {
    if (this.userContextId !== 0) {
      ContextualIdentityService.remove(this.userContextId);
--- a/browser_patches/firefox-stable/juggler/content/main.js
+++ b/browser_patches/firefox-stable/juggler/content/main.js
@ -69,6 +69,10 @@ const applySetting = {
  colorScheme: (colorScheme) => {
    frameTree.setColorScheme(colorScheme);
  },
+
+  reducedMotion: (reducedMotion) => {
+    frameTree.setReducedMotion(reducedMotion);
+  },
 };

 const channel = SimpleChannel.createForMessageManager('content::page', messageManager);
--- a/browser_patches/firefox-stable/juggler/protocol/BrowserHandler.js
+++ b/browser_patches/firefox-stable/juggler/protocol/BrowserHandler.js
@ -201,6 +201,10 @@ class BrowserHandler {
    await this._targetRegistry.browserContextForId(browserContextId).setColorScheme(nullToUndefined(colorScheme));
  }

+  async ['Browser.setReducedMotion']({browserContextId, reducedMotion}) {
+    await this._targetRegistry.browserContextForId(browserContextId).setReducedMotion(nullToUndefined(reducedMotion));
+  }
+
  async ['Browser.setVideoRecordingOptions']({browserContextId, dir, width, height, scale}) {
    await this._targetRegistry.browserContextForId(browserContextId).setVideoRecordingOptions({dir, width, height, scale});
  }
--- a/browser_patches/firefox-stable/juggler/protocol/PageHandler.js
+++ b/browser_patches/firefox-stable/juggler/protocol/PageHandler.js
@ -279,8 +279,9 @@ class PageHandler {
    return await this._contentPage.send('setFileInputFiles', options);
  }

-  async ['Page.setEmulatedMedia']({colorScheme, type}) {
+  async ['Page.setEmulatedMedia']({colorScheme, type, reducedMotion}) {
    this._pageTarget.setColorScheme(colorScheme || null);
+    this._pageTarget.setReducedMotion(reducedMotion || null);
    this._pageTarget.setEmulatedMedia(type);
  }

--- a/browser_patches/firefox-stable/juggler/protocol/Protocol.js
+++ b/browser_patches/firefox-stable/juggler/protocol/Protocol.js
@ -432,6 +432,12 @@ const Browser = {
        colorScheme: t.Nullable(t.Enum(['dark', 'light', 'no-preference'])),
      },
    },
+    'setReducedMotion': {
+      params: {
+        browserContextId: t.Optional(t.String),
+        reducedMotion: t.Nullable(t.Enum(['reduce', 'no-preference'])),
+      },
+    },
    'setVideoRecordingOptions': {
      params: {
        browserContextId: t.Optional(t.String),
@ -748,6 +754,7 @@ const Page = {
      params: {
        type: t.Optional(t.Enum(['screen', 'print', ''])),
        colorScheme: t.Optional(t.Enum(['dark', 'light', 'no-preference'])),
+        reducedMotion: t.Optional(t.Enum(['reduce', 'no-preference'])),
      },
    },
    'setCacheDisabled': {
--- a/browser_patches/firefox-stable/patches/bootstrap.diff
+++ b/browser_patches/firefox-stable/patches/bootstrap.diff
@ -171,8 +171,88 @@ index 040c7b124dec6bb254563bbe74fe50012cb077a3..b4e6b8132786af70e8ad0dce88b67c28
 
   const transportProvider = {
     setListener(upgradeListener) {
+diff --git a/docshell/base/BrowsingContext.cpp b/docshell/base/BrowsingContext.cpp
+index 24daf0c64b332823df7f5da698e35bab8edb72d5..6293aabbad9cb179ebbe8063e03496ca96d8577b 100644
+--- a/docshell/base/BrowsingContext.cpp
+++ b/docshell/base/BrowsingContext.cpp
+@@ -103,6 +103,13 @@ struct ParamTraits<mozilla::dom::PrefersColorSchemeOverride>
+           mozilla::dom::PrefersColorSchemeOverride::None,
+           mozilla::dom::PrefersColorSchemeOverride::EndGuard_> {};
+ 
+template <>
+struct ParamTraits<mozilla::dom::PrefersReducedMotionOverride>
+    : public ContiguousEnumSerializer<
+          mozilla::dom::PrefersReducedMotionOverride,
+          mozilla::dom::PrefersReducedMotionOverride::None,
+          mozilla::dom::PrefersReducedMotionOverride::EndGuard_> {};
+
+ template <>
+ struct ParamTraits<mozilla::dom::ExplicitActiveStatus>
+     : public ContiguousEnumSerializer<
+@@ -2537,6 +2544,23 @@ void BrowsingContext::DidSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+   });
+ }
+ 
+void BrowsingContext::DidSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+                             dom::PrefersReducedMotionOverride aOldValue) {
+  MOZ_ASSERT(IsTop());
+  if (PrefersReducedMotionOverride() == aOldValue) {
+    return;
+  }
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    if (nsIDocShell* shell = aContext->GetDocShell()) {
+      if (nsPresContext* pc = shell->GetPresContext()) {
+        pc->MediaFeatureValuesChanged(
+            {MediaFeatureChangeReason::SystemMetricsChange},
+            MediaFeatureChangePropagation::JustThisDocument);
+      }
+    }
+  });
+}
+
+ void BrowsingContext::DidSet(FieldIndex<IDX_MediumOverride>,
+                              nsString&& aOldValue) {
+   MOZ_ASSERT(IsTop());
+diff --git a/docshell/base/BrowsingContext.h b/docshell/base/BrowsingContext.h
+index fdd1fd88d2bb838ed88a8d49d1c923a7002893ee..6cd085d20da5692435cf7d9faaeeeec3b480ed83 100644
+--- a/docshell/base/BrowsingContext.h
+++ b/docshell/base/BrowsingContext.h
+@@ -191,6 +191,7 @@ enum class ExplicitActiveStatus : uint8_t {
+   FIELD(ServiceWorkersTestingEnabled, bool)                                   \
+   FIELD(MediumOverride, nsString)                                             \
+   FIELD(PrefersColorSchemeOverride, mozilla::dom::PrefersColorSchemeOverride) \
+  FIELD(PrefersReducedMotionOverride, mozilla::dom::PrefersReducedMotionOverride) \
+   FIELD(DisplayMode, mozilla::dom::DisplayMode)                               \
+   /* True if the top level browsing context owns a main media controller */   \
+   FIELD(HasMainMediaController, bool)                                         \
+@@ -810,6 +811,10 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
+     return GetPrefersColorSchemeOverride();
+   }
+ 
+  dom::PrefersReducedMotionOverride PrefersReducedMotionOverride() const {
+    return GetPrefersReducedMotionOverride();
+  }
+
+  protected:
+   virtual ~BrowsingContext();
+   BrowsingContext(WindowContext* aParentWindow, BrowsingContextGroup* aGroup,
+@@ -917,6 +922,14 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
+   void DidSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+               dom::PrefersColorSchemeOverride aOldValue);
+ 
+  bool CanSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+              dom::PrefersReducedMotionOverride, ContentParent*) {
+    return IsTop();
+  }
+
+  void DidSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+              dom::PrefersReducedMotionOverride aOldValue);
+
+   void DidSet(FieldIndex<IDX_MediumOverride>, nsString&& aOldValue);
+ 
+   bool CanSet(FieldIndex<IDX_SuspendMediaWhenInactive>, bool, ContentParent*) {
 diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
-index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0c33c37b9 100644
+index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..d4b3ef30d2a36f74fb17015b53b3a4d918e43160 100644
 --- a/docshell/base/nsDocShell.cpp
 +++ b/docshell/base/nsDocShell.cpp
@@ -15,6 +15,12 @@
@ -220,7 +300,7 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
 #include "nsNetCID.h"
 #include "nsNetUtil.h"
 #include "nsObjectLoadingContent.h"
-@@ -396,6 +406,12 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
+@@ -396,6 +406,13 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
       mAllowDNSPrefetch(true),
       mAllowWindowControl(true),
       mCSSErrorReportingEnabled(false),
@ -230,10 +310,11 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
 +      mForceActiveState(false),
 +      mOnlineOverride(nsIDocShell::ONLINE_OVERRIDE_NONE),
 +      mColorSchemeOverride(COLOR_SCHEME_OVERRIDE_NONE),
+      mReducedMotionOverride(REDUCED_MOTION_OVERRIDE_NONE),
       mAllowAuth(mItemType == typeContent),
       mAllowKeywordFixup(false),
       mDisableMetaRefreshWhenInactive(false),
-@@ -3345,6 +3361,203 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
+@@ -3345,6 +3362,221 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
   return NS_OK;
 }
 
@ -432,12 +513,30 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
 +  return NS_OK;
 +}
 +
+NS_IMETHODIMP
+nsDocShell::GetReducedMotionOverride(ReducedMotionOverride* aReducedMotionOverride) {
+  *aReducedMotionOverride = GetRootDocShell()->mReducedMotionOverride;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetReducedMotionOverride(ReducedMotionOverride aReducedMotionOverride) {
+  mReducedMotionOverride = aReducedMotionOverride;
+  RefPtr<nsPresContext> presContext = GetPresContext();
+  if (presContext) {
+    presContext->MediaFeatureValuesChanged(
+        {MediaFeatureChangeReason::SystemMetricsChange},
+        MediaFeatureChangePropagation::JustThisDocument);
+  }
+  return NS_OK;
+}
+
 +// =============== Juggler End =======================
 +
 NS_IMETHODIMP
 nsDocShell::GetIsNavigating(bool* aOut) {
   *aOut = mIsNavigating;
-@@ -4969,7 +5182,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
+@@ -4969,7 +5201,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
 }
 
 void nsDocShell::ActivenessMaybeChanged() {
@ -446,7 +545,7 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
   if (RefPtr<PresShell> presShell = GetPresShell()) {
     presShell->SetIsActive(isActive);
   }
-@@ -8708,6 +8921,12 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState) {
+@@ -8708,6 +8940,12 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState) {
                      true,  // aForceNoOpener
                      getter_AddRefs(newBC));
       MOZ_ASSERT(!newBC);
@ -459,7 +558,7 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
       return rv;
     }
 
-@@ -12707,6 +12926,9 @@ class OnLinkClickEvent : public Runnable {
+@@ -12707,6 +12945,9 @@ class OnLinkClickEvent : public Runnable {
       mHandler->OnLinkClickSync(mContent, mLoadState, mNoOpenerImplied,
                                 mTriggeringPrincipal);
     }
@ -469,7 +568,7 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
     return NS_OK;
   }
 
-@@ -12793,6 +13015,8 @@ nsresult nsDocShell::OnLinkClick(
+@@ -12793,6 +13034,8 @@ nsresult nsDocShell::OnLinkClick(
   nsCOMPtr<nsIRunnable> ev =
       new OnLinkClickEvent(this, aContent, loadState, noOpenerImplied,
                            aIsTrusted, aTriggeringPrincipal);
@ -479,7 +578,7 @@ index dffed2bfcca2ef93c0ee97129baa30743bf15b9f..de8cbb9884553088354b4f58c77ac5a0
 }
 
 diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
-index c29b1e05f3620a017156fd93d0928eca5e956859..4d89e1d5d2ebd3115fc06cfb1c7b6c08ea454d6d 100644
+index c29b1e05f3620a017156fd93d0928eca5e956859..7ca313920eb5693574de598f7de06fba796d2c77 100644
 --- a/docshell/base/nsDocShell.h
 +++ b/docshell/base/nsDocShell.h
@@ -14,6 +14,7 @@
@ -523,7 +622,7 @@ index c29b1e05f3620a017156fd93d0928eca5e956859..4d89e1d5d2ebd3115fc06cfb1c7b6c08
   // Handles retrieval of subframe session history for nsDocShell::LoadURI. If a
   // load is requested in a subframe of the current DocShell, the subframe
   // loadType may need to reflect the loadType of the parent document, or in
-@@ -1236,6 +1249,15 @@ class nsDocShell final : public nsDocLoader,
+@@ -1236,6 +1249,16 @@ class nsDocShell final : public nsDocLoader,
   bool mAllowDNSPrefetch : 1;
   bool mAllowWindowControl : 1;
   bool mCSSErrorReportingEnabled : 1;
@ -535,12 +634,13 @@ index c29b1e05f3620a017156fd93d0928eca5e956859..4d89e1d5d2ebd3115fc06cfb1c7b6c08
 +  RefPtr<nsGeolocationService> mGeolocationServiceOverride;
 +  OnlineOverride mOnlineOverride;
 +  ColorSchemeOverride mColorSchemeOverride;
+  ReducedMotionOverride mReducedMotionOverride;
 +
   bool mAllowAuth : 1;
   bool mAllowKeywordFixup : 1;
   bool mDisableMetaRefreshWhenInactive : 1;
 diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
-index d326491a03b83c4015f7bc3c779b0c5909e2db43..21f343bda776cd71212fc728d634dabcbe2d97da 100644
+index d326491a03b83c4015f7bc3c779b0c5909e2db43..828271c52ecdcecfc6c06fa9d85ffc19a9dcf28e 100644
 --- a/docshell/base/nsIDocShell.idl
 +++ b/docshell/base/nsIDocShell.idl
@@ -44,6 +44,7 @@ interface nsIURI;
@ -551,7 +651,7 @@ index d326491a03b83c4015f7bc3c779b0c5909e2db43..21f343bda776cd71212fc728d634dabc
 interface nsIEditor;
 interface nsIEditingSession;
 interface nsIInputStream;
-@@ -880,6 +881,35 @@ interface nsIDocShell : nsIDocShellTreeItem
+@@ -880,6 +881,42 @@ interface nsIDocShell : nsIDocShellTreeItem
    */
   void synchronizeLayoutHistoryState();
 
@ -582,13 +682,20 @@ index d326491a03b83c4015f7bc3c779b0c5909e2db43..21f343bda776cd71212fc728d634dabc
 +  };
 +  [infallible] attribute nsIDocShell_ColorSchemeOverride colorSchemeOverride;
 +
+  cenum ReducedMotionOverride : 8 {
+    REDUCED_MOTION_OVERRIDE_REDUCE,
+    REDUCED_MOTION_OVERRIDE_NO_PREFERENCE,
+    REDUCED_MOTION_OVERRIDE_NONE, /* This clears the override. */
+  };
+  [infallible] attribute nsIDocShell_ReducedMotionOverride reducedMotionOverride;
+
 +  void setGeolocationOverride(in nsIDOMGeoPosition position);
 +
   /**
    * This attempts to save any applicable layout history state (like
    * scroll position) in the nsISHEntry. This is normally done
 diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
-index 93baac5ba84922575d8d334533f553f3ad69cfa0..eb4ae377a31301b2df1d06ed63b331b7ba849c9c 100644
+index 93baac5ba84922575d8d334533f553f3ad69cfa0..248207e95ab683af1e4f1fd2d53b7eb7d9a49c69 100644
 --- a/dom/base/Document.cpp
 +++ b/dom/base/Document.cpp
@@ -3496,6 +3496,9 @@ void Document::SendToConsole(nsCOMArray<nsISecurityConsoleMessage>& aMessages) {
@ -644,6 +751,59 @@ index 93baac5ba84922575d8d334533f553f3ad69cfa0..eb4ae377a31301b2df1d06ed63b331b7
   if (aIgnoreRFP == IgnoreRFP::No &&
       nsContentUtils::ShouldResistFingerprinting(this)) {
     return StylePrefersColorScheme::Light;
+@@ -17012,6 +17037,39 @@ StylePrefersColorScheme Document::PrefersColorScheme(
+   return dark ? StylePrefersColorScheme::Dark : StylePrefersColorScheme::Light;
+ }
+ 
+bool Document::PrefersReducedMotion() const {
+  auto* docShell = static_cast<nsDocShell*>(GetDocShell());
+  nsIDocShell::ReducedMotionOverride reducedMotion;
+  if (docShell && docShell->GetReducedMotionOverride(&reducedMotion) == NS_OK &&
+      reducedMotion != nsIDocShell::REDUCED_MOTION_OVERRIDE_NONE) {
+    switch (reducedMotion) {
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_REDUCE:
+        return true;
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_NO_PREFERENCE:
+        return false;
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_NONE:
+        break;
+    };
+  }
+
+  if (auto* bc = GetBrowsingContext()) {
+    switch (bc->Top()->PrefersReducedMotionOverride()) {
+      case dom::PrefersReducedMotionOverride::Reduce:
+        return true;
+      case dom::PrefersReducedMotionOverride::No_preference:
+        return false;
+      case dom::PrefersReducedMotionOverride::None:
+      case dom::PrefersReducedMotionOverride::EndGuard_:
+        break;
+    }
+  }
+
+  if (nsContentUtils::ShouldResistFingerprinting(this)) {
+    return false;
+  }
+  return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+}
+
+ // static
+ bool Document::UseOverlayScrollbars(const Document* aDocument) {
+   BrowsingContext* bc = aDocument ? aDocument->GetBrowsingContext() : nullptr;
+diff --git a/dom/base/Document.h b/dom/base/Document.h
+index 87807e615c6897d92f3f8a7d7409e690c039f72d..54882eb8b82a9727022ca39371a9cc27d2c5ef75 100644
+--- a/dom/base/Document.h
+++ b/dom/base/Document.h
+@@ -4013,6 +4013,8 @@ class Document : public nsINode,
+   enum class IgnoreRFP { No, Yes };
+   StylePrefersColorScheme PrefersColorScheme(IgnoreRFP = IgnoreRFP::No) const;
+ 
+  bool PrefersReducedMotion() const;
+
+   // Returns true if we use overlay scrollbars on the system wide or on the
+   // given document.
+   static bool UseOverlayScrollbars(const Document* aDocument);
 diff --git a/dom/base/Navigator.cpp b/dom/base/Navigator.cpp
 index 407eecefd4e1cdf58f63714783ecf18cc6e28dce..a479467953fdfb54fb5183ce86794339aa36ca9a 100644
 --- a/dom/base/Navigator.cpp
@ -996,6 +1156,36 @@ index b53d2f740b5901e4422fa3af84198dc687c535d9..052d15cccb021540cc9c7dfe5a9337d9
   static void ResetTimeZone();
 
   static bool DumpEnabled();
+diff --git a/dom/chrome-webidl/BrowsingContext.webidl b/dom/chrome-webidl/BrowsingContext.webidl
+index dfdfe724ccc52dd3a95997383a67b296822af2fb..82c1e391ae05d84286723710f4915e435ea6bb38 100644
+--- a/dom/chrome-webidl/BrowsingContext.webidl
+++ b/dom/chrome-webidl/BrowsingContext.webidl
+@@ -51,6 +51,15 @@ enum PrefersColorSchemeOverride {
+   "dark",
+ };
+ 
+/**
+ * CSS prefers-reduced-motion values.
+ */
+enum PrefersReducedMotionOverride {
+  "none",
+  "reduce",
+  "no-preference",
+};
+
+ /**
+  * Allowed overrides of platform/pref default behaviour for touch events.
+  */
+@@ -173,6 +182,9 @@ interface BrowsingContext {
+   // Color-scheme simulation, for DevTools.
+   [SetterThrows] attribute PrefersColorSchemeOverride prefersColorSchemeOverride;
+ 
+  // Reduced-Motion simulation, for DevTools.
+  [SetterThrows] attribute PrefersReducedMotionOverride prefersReducedMotionOverride;
+
+   /**
+    * A unique identifier for the browser element that is hosting this
+    * BrowsingContext tree. Every BrowsingContext in the element's tree will
 diff --git a/dom/geolocation/Geolocation.cpp b/dom/geolocation/Geolocation.cpp
 index 763192a50cf8dce36eaf1fd2b470c631eecfe65c..436f01a2ca6166f1a97139f1cda7e1832b9df36c 100644
 --- a/dom/geolocation/Geolocation.cpp
@ -1667,6 +1857,22 @@ index 77b4c4ea3581e3b66b0b40dae33c807b2d5aefd8..84af4461b9e946122527ac974dc30da5
   void updateTimeZone();
 
   void internalResyncICUDefaultTimeZone();
+diff --git a/layout/style/nsMediaFeatures.cpp b/layout/style/nsMediaFeatures.cpp
+index 445a031b11c6e3c65ed859a03a83a21da88f1472..87e14f7208b5b9348c13dcb07b43e2dff25e4fd9 100644
+--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
+@@ -261,10 +261,7 @@ nsAtom* Gecko_MediaFeatures_GetOperatingSystemVersion(
+ }
+ 
+ bool Gecko_MediaFeatures_PrefersReducedMotion(const Document* aDocument) {
+-  if (nsContentUtils::ShouldResistFingerprinting(aDocument)) {
+-    return false;
+-  }
+-  return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+  return aDocument->PrefersReducedMotion();
+ }
+ 
+ StylePrefersColorScheme Gecko_MediaFeatures_PrefersColorScheme(
 diff --git a/media/libjpeg/jconfig.h b/media/libjpeg/jconfig.h
 index f2723e654098ff27542e1eb16a536c11ad0af617..b0b480551ff7d895dfdeb5a9800874858929c8ba 100644
 --- a/media/libjpeg/jconfig.h
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@ -1,2 +1,2 @@
-1263
-Changed: aslushnikov@gmail.com Mon 14 May 2021 21:37:09 PM PDT
+1264
+Changed: max@schmitt.mx Di 18. Mai 20:50:35 CEST 2021
--- a/browser_patches/firefox/juggler/TargetRegistry.js
+++ b/browser_patches/firefox/juggler/TargetRegistry.js
@ -159,6 +159,7 @@ class TargetRegistry {
      target.updateUserAgent();
      target.updateTouchOverride();
      target.updateColorSchemeOverride();
+      target.updateReducedMotionOverride();
      if (!hasExplicitSize)
        target.updateViewportSize();
      if (browserContext.videoRecordingOptions)
@ -437,6 +438,14 @@ class PageTarget {
    this._linkedBrowser.browsingContext.prefersColorSchemeOverride = this.colorScheme || this._browserContext.colorScheme || 'none';
  }

+  setReducedMotion(reducedMotion) {
+    this.reducedMotion = fromProtocolReducedMotion(reducedMotion);
+    this.updateReducedMotionOverride();
+  }
+
+  updateReducedMotionOverride() {
+    this._linkedBrowser.browsingContext.prefersReducedMotionOverride = this.reducedMotion || this._browserContext.reducedMotion || 'none';
+  }

  async setViewportSize(viewportSize) {
    this._viewportSize = viewportSize;
@ -612,6 +621,14 @@ function fromProtocolColorScheme(colorScheme) {
  throw new Error('Unknown color scheme: ' + colorScheme);
 }

+function fromProtocolReducedMotion(reducedMotion) {
+  if (reducedMotion === 'reduce')
+    return reducedMotion;
+  if (reducedMotion === null || reducedMotion === 'no-preference')
+    return undefined;
+  throw new Error('Unknown reduced motion: ' + reducedMotion);
+}
+
 class BrowserContext {
  constructor(registry, browserContextId, removeOnDetach) {
    this._registry = registry;
@ -639,6 +656,7 @@ class BrowserContext {
    this.defaultUserAgent = null;
    this.touchOverride = false;
    this.colorScheme = 'none';
+    this.reducedMotion = 'none';
    this.videoRecordingOptions = undefined;
    this.scriptsToEvaluateOnNewDocument = [];
    this.bindings = [];
@ -652,6 +670,12 @@ class BrowserContext {
      page.updateColorSchemeOverride();
  }

+  setReducedMotion(reducedMotion) {
+    this.reducedMotion = fromProtocolReducedMotion(reducedMotion);
+    for (const page of this.pages)
+      page.updateReducedMotionOverride();
+  }
+
  async destroy() {
    if (this.userContextId !== 0) {
      ContextualIdentityService.remove(this.userContextId);
--- a/browser_patches/firefox/juggler/content/main.js
+++ b/browser_patches/firefox/juggler/content/main.js
@ -69,6 +69,10 @@ const applySetting = {
  colorScheme: (colorScheme) => {
    frameTree.setColorScheme(colorScheme);
  },
+
+  reducedMotion: (reducedMotion) => {
+    frameTree.setReducedMotion(reducedMotion);
+  },
 };

 const channel = SimpleChannel.createForMessageManager('content::page', messageManager);
--- a/browser_patches/firefox/juggler/protocol/BrowserHandler.js
+++ b/browser_patches/firefox/juggler/protocol/BrowserHandler.js
@ -201,6 +201,10 @@ class BrowserHandler {
    await this._targetRegistry.browserContextForId(browserContextId).setColorScheme(nullToUndefined(colorScheme));
  }

+  async ['Browser.setReducedMotion']({browserContextId, reducedMotion}) {
+    await this._targetRegistry.browserContextForId(browserContextId).setReducedMotion(nullToUndefined(reducedMotion));
+  }
+
  async ['Browser.setVideoRecordingOptions']({browserContextId, dir, width, height, scale}) {
    await this._targetRegistry.browserContextForId(browserContextId).setVideoRecordingOptions({dir, width, height, scale});
  }
--- a/browser_patches/firefox/juggler/protocol/PageHandler.js
+++ b/browser_patches/firefox/juggler/protocol/PageHandler.js
@ -279,8 +279,9 @@ class PageHandler {
    return await this._contentPage.send('setFileInputFiles', options);
  }

-  async ['Page.setEmulatedMedia']({colorScheme, type}) {
+  async ['Page.setEmulatedMedia']({colorScheme, type, reducedMotion}) {
    this._pageTarget.setColorScheme(colorScheme || null);
+    this._pageTarget.setReducedMotion(reducedMotion || null);
    this._pageTarget.setEmulatedMedia(type);
  }

--- a/browser_patches/firefox/juggler/protocol/Protocol.js
+++ b/browser_patches/firefox/juggler/protocol/Protocol.js
@ -432,6 +432,12 @@ const Browser = {
        colorScheme: t.Nullable(t.Enum(['dark', 'light', 'no-preference'])),
      },
    },
+    'setReducedMotion': {
+      params: {
+        browserContextId: t.Optional(t.String),
+        reducedMotion: t.Nullable(t.Enum(['reduce', 'no-preference'])),
+      },
+    },
    'setVideoRecordingOptions': {
      params: {
        browserContextId: t.Optional(t.String),
@ -748,6 +754,7 @@ const Page = {
      params: {
        type: t.Optional(t.Enum(['screen', 'print', ''])),
        colorScheme: t.Optional(t.Enum(['dark', 'light', 'no-preference'])),
+        reducedMotion: t.Optional(t.Enum(['reduce', 'no-preference'])),
      },
    },
    'setCacheDisabled': {
--- a/browser_patches/firefox/patches/bootstrap.diff
+++ b/browser_patches/firefox/patches/bootstrap.diff
@ -171,8 +171,88 @@ index 040c7b124dec6bb254563bbe74fe50012cb077a3..b4e6b8132786af70e8ad0dce88b67c28
 
   const transportProvider = {
     setListener(upgradeListener) {
+diff --git a/docshell/base/BrowsingContext.cpp b/docshell/base/BrowsingContext.cpp
+index f3292d8ae6da1865847ded8b1c79a80ba8fca70e..cf8fa57ce2363555d10c837c99efd282d515e64b 100644
+--- a/docshell/base/BrowsingContext.cpp
+++ b/docshell/base/BrowsingContext.cpp
+@@ -105,6 +105,13 @@ struct ParamTraits<mozilla::dom::PrefersColorSchemeOverride>
+           mozilla::dom::PrefersColorSchemeOverride::None,
+           mozilla::dom::PrefersColorSchemeOverride::EndGuard_> {};
+ 
+template <>
+struct ParamTraits<mozilla::dom::PrefersReducedMotionOverride>
+    : public ContiguousEnumSerializer<
+          mozilla::dom::PrefersReducedMotionOverride,
+          mozilla::dom::PrefersReducedMotionOverride::None,
+          mozilla::dom::PrefersReducedMotionOverride::EndGuard_> {};
+
+ template <>
+ struct ParamTraits<mozilla::dom::ExplicitActiveStatus>
+     : public ContiguousEnumSerializer<
+@@ -2637,6 +2644,23 @@ void BrowsingContext::DidSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+   });
+ }
+ 
+void BrowsingContext::DidSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+                             dom::PrefersReducedMotionOverride aOldValue) {
+  MOZ_ASSERT(IsTop());
+  if (PrefersReducedMotionOverride() == aOldValue) {
+    return;
+  }
+  PreOrderWalk([&](BrowsingContext* aContext) {
+    if (nsIDocShell* shell = aContext->GetDocShell()) {
+      if (nsPresContext* pc = shell->GetPresContext()) {
+        pc->MediaFeatureValuesChanged(
+            {MediaFeatureChangeReason::SystemMetricsChange},
+            MediaFeatureChangePropagation::JustThisDocument);
+      }
+    }
+  });
+}
+
+ void BrowsingContext::DidSet(FieldIndex<IDX_MediumOverride>,
+                              nsString&& aOldValue) {
+   MOZ_ASSERT(IsTop());
+diff --git a/docshell/base/BrowsingContext.h b/docshell/base/BrowsingContext.h
+index ba3cceb7c9d6bc0014c1abf66d5b19d6d26a45db..d41680af40fe44ba1db2bff5946c902db7373225 100644
+--- a/docshell/base/BrowsingContext.h
+++ b/docshell/base/BrowsingContext.h
+@@ -191,6 +191,7 @@ enum class ExplicitActiveStatus : uint8_t {
+   FIELD(ServiceWorkersTestingEnabled, bool)                                   \
+   FIELD(MediumOverride, nsString)                                             \
+   FIELD(PrefersColorSchemeOverride, mozilla::dom::PrefersColorSchemeOverride) \
+  FIELD(PrefersReducedMotionOverride, mozilla::dom::PrefersReducedMotionOverride) \
+   FIELD(DisplayMode, mozilla::dom::DisplayMode)                               \
+   /* True if the top level browsing context owns a main media controller */   \
+   FIELD(HasMainMediaController, bool)                                         \
+@@ -847,6 +848,10 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
+     return GetPrefersColorSchemeOverride();
+   }
+ 
+  dom::PrefersReducedMotionOverride PrefersReducedMotionOverride() const {
+    return GetPrefersReducedMotionOverride();
+  }
+
+   void FlushSessionStore();
+ 
+  protected:
+@@ -961,6 +966,14 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
+   void DidSet(FieldIndex<IDX_PrefersColorSchemeOverride>,
+               dom::PrefersColorSchemeOverride aOldValue);
+ 
+  bool CanSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+              dom::PrefersReducedMotionOverride, ContentParent*) {
+    return IsTop();
+  }
+
+  void DidSet(FieldIndex<IDX_PrefersReducedMotionOverride>,
+              dom::PrefersReducedMotionOverride aOldValue);
+
+   void DidSet(FieldIndex<IDX_MediumOverride>, nsString&& aOldValue);
+ 
+   bool CanSet(FieldIndex<IDX_SuspendMediaWhenInactive>, bool, ContentParent*) {
 diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
-index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc9323603d 100644
+index d99ddc3181cf9092633558ac5798f38860ad4f7d..52ff3ddb06b7714469b695b3c894172c33af0c83 100644
 --- a/docshell/base/nsDocShell.cpp
 +++ b/docshell/base/nsDocShell.cpp
@@ -15,6 +15,12 @@
@ -220,7 +300,7 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
 #include "nsNetCID.h"
 #include "nsNetUtil.h"
 #include "nsObjectLoadingContent.h"
-@@ -397,6 +407,12 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
+@@ -397,6 +407,13 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
       mAllowDNSPrefetch(true),
       mAllowWindowControl(true),
       mCSSErrorReportingEnabled(false),
@ -230,10 +310,11 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
 +      mForceActiveState(false),
 +      mOnlineOverride(nsIDocShell::ONLINE_OVERRIDE_NONE),
 +      mColorSchemeOverride(COLOR_SCHEME_OVERRIDE_NONE),
+      mReducedMotionOverride(REDUCED_MOTION_OVERRIDE_NONE),
       mAllowAuth(mItemType == typeContent),
       mAllowKeywordFixup(false),
       mDisableMetaRefreshWhenInactive(false),
-@@ -3328,6 +3344,203 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
+@@ -3328,6 +3345,221 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
   return NS_OK;
 }
 
@ -432,12 +513,30 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
 +  return NS_OK;
 +}
 +
+NS_IMETHODIMP
+nsDocShell::GetReducedMotionOverride(ReducedMotionOverride* aReducedMotionOverride) {
+  *aReducedMotionOverride = GetRootDocShell()->mReducedMotionOverride;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetReducedMotionOverride(ReducedMotionOverride aReducedMotionOverride) {
+  mReducedMotionOverride = aReducedMotionOverride;
+  RefPtr<nsPresContext> presContext = GetPresContext();
+  if (presContext) {
+    presContext->MediaFeatureValuesChanged(
+        {MediaFeatureChangeReason::SystemMetricsChange},
+        MediaFeatureChangePropagation::JustThisDocument);
+  }
+  return NS_OK;
+}
+
 +// =============== Juggler End =======================
 +
 NS_IMETHODIMP
 nsDocShell::GetIsNavigating(bool* aOut) {
   *aOut = mIsNavigating;
-@@ -4952,7 +5165,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
+@@ -4952,7 +5184,7 @@ nsDocShell::GetVisibility(bool* aVisibility) {
 }
 
 void nsDocShell::ActivenessMaybeChanged() {
@ -446,7 +545,7 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
   if (RefPtr<PresShell> presShell = GetPresShell()) {
     presShell->SetIsActive(isActive);
   }
-@@ -8675,6 +8888,12 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState) {
+@@ -8675,6 +8907,12 @@ nsresult nsDocShell::PerformRetargeting(nsDocShellLoadState* aLoadState) {
                      true,  // aForceNoOpener
                      getter_AddRefs(newBC));
       MOZ_ASSERT(!newBC);
@ -459,7 +558,7 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
       return rv;
     }
 
-@@ -12691,6 +12910,9 @@ class OnLinkClickEvent : public Runnable {
+@@ -12691,6 +12929,9 @@ class OnLinkClickEvent : public Runnable {
       mHandler->OnLinkClickSync(mContent, mLoadState, mNoOpenerImplied,
                                 mTriggeringPrincipal);
     }
@ -469,7 +568,7 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
     return NS_OK;
   }
 
-@@ -12769,6 +12991,8 @@ nsresult nsDocShell::OnLinkClick(
+@@ -12769,6 +13010,8 @@ nsresult nsDocShell::OnLinkClick(
   nsCOMPtr<nsIRunnable> ev =
       new OnLinkClickEvent(this, aContent, loadState, noOpenerImplied,
                            aIsTrusted, aTriggeringPrincipal);
@ -479,7 +578,7 @@ index d99ddc3181cf9092633558ac5798f38860ad4f7d..6fbeec60b7ff51e5591c8e8c50e713bc
 }
 
 diff --git a/docshell/base/nsDocShell.h b/docshell/base/nsDocShell.h
-index cde10e9424f0a97cf57ae740e1651731b8d8ac1c..7acba6e28134066a7a3f010e2f8a35cd3646396f 100644
+index cde10e9424f0a97cf57ae740e1651731b8d8ac1c..89542ee3def7115b22d36bdb3fb61da308ea3a37 100644
 --- a/docshell/base/nsDocShell.h
 +++ b/docshell/base/nsDocShell.h
@@ -14,6 +14,7 @@
@ -523,7 +622,7 @@ index cde10e9424f0a97cf57ae740e1651731b8d8ac1c..7acba6e28134066a7a3f010e2f8a35cd
   // Handles retrieval of subframe session history for nsDocShell::LoadURI. If a
   // load is requested in a subframe of the current DocShell, the subframe
   // loadType may need to reflect the loadType of the parent document, or in
-@@ -1232,6 +1245,15 @@ class nsDocShell final : public nsDocLoader,
+@@ -1232,6 +1245,16 @@ class nsDocShell final : public nsDocLoader,
   bool mAllowDNSPrefetch : 1;
   bool mAllowWindowControl : 1;
   bool mCSSErrorReportingEnabled : 1;
@ -535,12 +634,13 @@ index cde10e9424f0a97cf57ae740e1651731b8d8ac1c..7acba6e28134066a7a3f010e2f8a35cd
 +  RefPtr<nsGeolocationService> mGeolocationServiceOverride;
 +  OnlineOverride mOnlineOverride;
 +  ColorSchemeOverride mColorSchemeOverride;
+  ReducedMotionOverride mReducedMotionOverride;
 +
   bool mAllowAuth : 1;
   bool mAllowKeywordFixup : 1;
   bool mDisableMetaRefreshWhenInactive : 1;
 diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
-index dcf0b8c00d70a08fdd5cbe07c30e415968cd9e3e..5fe27677654bb4527b5103a6d01a709fc8688b6b 100644
+index dcf0b8c00d70a08fdd5cbe07c30e415968cd9e3e..8ae4de4d5255bbbaa8cd270e50cb320248e35f33 100644
 --- a/docshell/base/nsIDocShell.idl
 +++ b/docshell/base/nsIDocShell.idl
@@ -44,6 +44,7 @@ interface nsIURI;
@ -551,7 +651,7 @@ index dcf0b8c00d70a08fdd5cbe07c30e415968cd9e3e..5fe27677654bb4527b5103a6d01a709f
 interface nsIEditor;
 interface nsIEditingSession;
 interface nsIInputStream;
-@@ -855,6 +856,35 @@ interface nsIDocShell : nsIDocShellTreeItem
+@@ -855,6 +856,42 @@ interface nsIDocShell : nsIDocShellTreeItem
    */
   void synchronizeLayoutHistoryState();
 
@ -582,13 +682,20 @@ index dcf0b8c00d70a08fdd5cbe07c30e415968cd9e3e..5fe27677654bb4527b5103a6d01a709f
 +  };
 +  [infallible] attribute nsIDocShell_ColorSchemeOverride colorSchemeOverride;
 +
+  cenum ReducedMotionOverride : 8 {
+    REDUCED_MOTION_OVERRIDE_REDUCE,
+    REDUCED_MOTION_OVERRIDE_NO_PREFERENCE,
+    REDUCED_MOTION_OVERRIDE_NONE, /* This clears the override. */
+  };
+  [infallible] attribute nsIDocShell_ReducedMotionOverride reducedMotionOverride;
+
 +  void setGeolocationOverride(in nsIDOMGeoPosition position);
 +
   /**
    * This attempts to save any applicable layout history state (like
    * scroll position) in the nsISHEntry. This is normally done
 diff --git a/dom/base/Document.cpp b/dom/base/Document.cpp
-index ce2cbca4b4c5ebb95a0991793131aa53317b862b..7f5a9653f97e3e27c96f8be7cda039f4d2ad5093 100644
+index ce2cbca4b4c5ebb95a0991793131aa53317b862b..2a016e0e5f658043c5ea14b0ead95da7ca5c963c 100644
 --- a/dom/base/Document.cpp
 +++ b/dom/base/Document.cpp
@@ -3490,6 +3490,9 @@ void Document::SendToConsole(nsCOMArray<nsISecurityConsoleMessage>& aMessages) {
@ -644,6 +751,59 @@ index ce2cbca4b4c5ebb95a0991793131aa53317b862b..7f5a9653f97e3e27c96f8be7cda039f4
   if (aIgnoreRFP == IgnoreRFP::No &&
       nsContentUtils::ShouldResistFingerprinting(this)) {
     return StylePrefersColorScheme::Light;
+@@ -17111,6 +17136,39 @@ StylePrefersColorScheme Document::PrefersColorScheme(
+   return dark ? StylePrefersColorScheme::Dark : StylePrefersColorScheme::Light;
+ }
+ 
+bool Document::PrefersReducedMotion() const {
+  auto* docShell = static_cast<nsDocShell*>(GetDocShell());
+  nsIDocShell::ReducedMotionOverride reducedMotion;
+  if (docShell && docShell->GetReducedMotionOverride(&reducedMotion) == NS_OK &&
+      reducedMotion != nsIDocShell::REDUCED_MOTION_OVERRIDE_NONE) {
+    switch (reducedMotion) {
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_REDUCE:
+        return true;
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_NO_PREFERENCE:
+        return false;
+      case nsIDocShell::REDUCED_MOTION_OVERRIDE_NONE:
+        break;
+    };
+  }
+
+  if (auto* bc = GetBrowsingContext()) {
+    switch (bc->Top()->PrefersReducedMotionOverride()) {
+      case dom::PrefersReducedMotionOverride::Reduce:
+        return true;
+      case dom::PrefersReducedMotionOverride::No_preference:
+        return false;
+      case dom::PrefersReducedMotionOverride::None:
+      case dom::PrefersReducedMotionOverride::EndGuard_:
+        break;
+    }
+  }
+
+  if (nsContentUtils::ShouldResistFingerprinting(this)) {
+    return false;
+  }
+  return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+}
+
+ // static
+ bool Document::UseOverlayScrollbars(const Document* aDocument) {
+   BrowsingContext* bc = aDocument ? aDocument->GetBrowsingContext() : nullptr;
+diff --git a/dom/base/Document.h b/dom/base/Document.h
+index e5bf988011e6fdbcac6d54c596769b15da3077ae..e2c9f12828be70a116e3e74f2fef402a5441e84d 100644
+--- a/dom/base/Document.h
+++ b/dom/base/Document.h
+@@ -3995,6 +3995,8 @@ class Document : public nsINode,
+   enum class IgnoreRFP { No, Yes };
+   StylePrefersColorScheme PrefersColorScheme(IgnoreRFP = IgnoreRFP::No) const;
+ 
+  bool PrefersReducedMotion() const;
+
+   // Returns true if we use overlay scrollbars on the system wide or on the
+   // given document.
+   static bool UseOverlayScrollbars(const Document* aDocument);
 diff --git a/dom/base/Navigator.cpp b/dom/base/Navigator.cpp
 index b21d872fba4a79c946d0b1501585b911f29d4e94..b2dfdddd9dc2110f9c80b57dfdf98ce8b3583551 100644
 --- a/dom/base/Navigator.cpp
@ -996,6 +1156,36 @@ index c47a5a8c78bd28e4a5afa048cd56ad762a7a684f..4007a192ecee88d6246f8245f11278f7
   static void ResetTimeZone();
 
   static bool DumpEnabled();
+diff --git a/dom/chrome-webidl/BrowsingContext.webidl b/dom/chrome-webidl/BrowsingContext.webidl
+index 60c6bf107402fbcdcbc646451b4f92fae4be41d5..9f70659f20f06039ea396af6ac781239218c2ae4 100644
+--- a/dom/chrome-webidl/BrowsingContext.webidl
+++ b/dom/chrome-webidl/BrowsingContext.webidl
+@@ -52,6 +52,15 @@ enum PrefersColorSchemeOverride {
+   "dark",
+ };
+ 
+/**
+ * CSS prefers-reduced-motion values.
+ */
+enum PrefersReducedMotionOverride {
+  "none",
+  "reduce",
+  "no-preference",
+};
+
+ /**
+  * Allowed overrides of platform/pref default behaviour for touch events.
+  */
+@@ -175,6 +184,9 @@ interface BrowsingContext {
+   // Color-scheme simulation, for DevTools.
+   [SetterThrows] attribute PrefersColorSchemeOverride prefersColorSchemeOverride;
+ 
+  // Reduced-Motion simulation, for DevTools.
+  [SetterThrows] attribute PrefersReducedMotionOverride prefersReducedMotionOverride;
+
+   /**
+    * A unique identifier for the browser element that is hosting this
+    * BrowsingContext tree. Every BrowsingContext in the element's tree will
 diff --git a/dom/geolocation/Geolocation.cpp b/dom/geolocation/Geolocation.cpp
 index 763192a50cf8dce36eaf1fd2b470c631eecfe65c..436f01a2ca6166f1a97139f1cda7e1832b9df36c 100644
 --- a/dom/geolocation/Geolocation.cpp
@ -1667,6 +1857,22 @@ index 77b4c4ea3581e3b66b0b40dae33c807b2d5aefd8..84af4461b9e946122527ac974dc30da5
   void updateTimeZone();
 
   void internalResyncICUDefaultTimeZone();
+diff --git a/layout/style/nsMediaFeatures.cpp b/layout/style/nsMediaFeatures.cpp
+index fffe37c359c5ba3a4e8cb4a44256f2c69182885b..8fcd8a1fa3e07f6c712b67247e303e624d316a69 100644
+--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
+@@ -246,10 +246,7 @@ nsAtom* Gecko_MediaFeatures_GetOperatingSystemVersion(
+ }
+ 
+ bool Gecko_MediaFeatures_PrefersReducedMotion(const Document* aDocument) {
+-  if (nsContentUtils::ShouldResistFingerprinting(aDocument)) {
+-    return false;
+-  }
+-  return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
+  return aDocument->PrefersReducedMotion();
+ }
+ 
+ StylePrefersColorScheme Gecko_MediaFeatures_PrefersColorScheme(
 diff --git a/media/libjpeg/jconfig.h b/media/libjpeg/jconfig.h
 index f2723e654098ff27542e1eb16a536c11ad0af617..b0b480551ff7d895dfdeb5a9800874858929c8ba 100644
 --- a/media/libjpeg/jconfig.h