--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -38,17 +38,17 @@
 #include "nsThreadUtils.h"
 #include "nsFrameManager.h"
 #include "nsLayoutUtils.h"
 #include "nsViewManager.h"
 #include "mozilla/GeckoRestyleManager.h"
 #include "mozilla/RestyleManager.h"
 #include "mozilla/RestyleManagerInlines.h"
 #include "SurfaceCacheUtils.h"
-#include "nsCSSRuleProcessor.h"
+#include "nsMediaFeatures.h"
 #include "nsRuleNode.h"
 #include "gfxPlatform.h"
 #include "nsCSSRules.h"
 #include "nsFontFaceLoader.h"
 #include "mozilla/EffectCompositor.h"
 #include "mozilla/EventListenerManager.h"
 #include "prenv.h"
 #include "nsPluginFrame.h"
@@ -1889,17 +1889,17 @@ nsPresContext::SysColorChangedInternal()
   RebuildAllStyleData(nsChangeHint(0), nsRestyleHint(0));
 }
 
 void
 nsPresContext::RefreshSystemMetrics()
 {
   // This will force the system metrics to be generated the next time they're
   // used.
-  nsCSSRuleProcessor::FreeSystemMetrics();
+  nsMediaFeatures::FreeSystemMetrics();
 
   // Changes to system metrics can change media queries on them.
   //
   // Changes in theme can change system colors (whose changes are
   // properly reflected in computed style data), system fonts (whose
   // changes are not), and -moz-appearance (whose changes likewise are
   // not), so we need to recascade for the first, and reflow for the rest.
   MediaFeatureValuesChanged(eRestyle_ForceDescendants, NS_STYLE_HINT_REFLOW);

--- a/layout/build/nsLayoutStatics.cpp
+++ b/layout/build/nsLayoutStatics.cpp
@@ -45,17 +45,17 @@
 #include "nsTextControlFrame.h"
 #include "nsXBLService.h"
 #include "txMozillaXSLTProcessor.h"
 #include "nsTreeSanitizer.h"
 #include "nsCellMap.h"
 #include "nsTextFrame.h"
 #include "nsCCUncollectableMarker.h"
 #include "nsTextFragment.h"
-#include "nsCSSRuleProcessor.h"
+#include "nsMediaFeatures.h"
 #include "nsCORSListenerProxy.h"
 #include "nsHTMLDNSPrefetch.h"
 #include "nsHtml5Module.h"
 #include "nsHTMLTags.h"
 #include "nsIRDFContentSink.h"	// for RDF atom initialization
 #include "mozilla/dom/FallbackEncoding.h"
 #include "nsFocusManager.h"
 #include "nsListControlFrame.h"
@@ -334,17 +334,17 @@ nsLayoutStatics::Shutdown()
   nsXULPopupManager::Shutdown();
 #endif
   StorageObserver::Shutdown();
   txMozillaXSLTProcessor::Shutdown();
   Attr::Shutdown();
   EventListenerManager::Shutdown();
   IMEStateManager::Shutdown();
   nsCSSParser::Shutdown();
-  nsCSSRuleProcessor::Shutdown();
+  nsMediaFeatures::Shutdown();
   nsHTMLDNSPrefetch::Shutdown();
   nsCSSRendering::Shutdown();
   StaticPresData::Shutdown();
 #ifdef DEBUG
   nsFrame::DisplayReflowShutdown();
 #endif
   nsCellMap::Shutdown();
   ActiveLayerTracker::Shutdown();

--- a/layout/style/ServoStyleSet.cpp
+++ b/layout/style/ServoStyleSet.cpp
@@ -19,21 +19,21 @@
 #include "mozilla/dom/AnonymousContent.h"
 #include "mozilla/dom/ChildIterator.h"
 #include "mozilla/dom/FontFaceSet.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/ElementInlines.h"
 #include "nsCSSAnonBoxes.h"
 #include "nsCSSFrameConstructor.h"
 #include "nsCSSPseudoElements.h"
-#include "nsCSSRuleProcessor.h"
 #include "nsDeviceContext.h"
 #include "nsHTMLStyleSheet.h"
 #include "nsIAnonymousContentCreator.h"
 #include "nsIDocumentInlines.h"
+#include "nsMediaFeatures.h"
 #include "nsPrintfCString.h"
 #include "nsSMILAnimationController.h"
 #include "nsStyleContext.h"
 #include "nsStyleSet.h"
 #include "gfxUserFontSet.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -409,17 +409,17 @@ ServoStyleSet::PreTraverseSync()
 {
   // Get the Document's root element to ensure that the cache is valid before
   // calling into the (potentially-parallel) Servo traversal, where a cache hit
   // is necessary to avoid a data race when updating the cache.
   mozilla::Unused << mPresContext->Document()->GetRootElement();
 
   ResolveMappedAttrDeclarationBlocks();
 
-  nsCSSRuleProcessor::InitSystemMetrics();
+  nsMediaFeatures::InitSystemMetrics();
 
   LookAndFeel::NativeInit();
 
   // This is lazily computed and pseudo matching needs to access
   // it so force computation early.
   mPresContext->Document()->GetDocumentState();
 
   if (gfxUserFontSet* userFontSet = mPresContext->Document()->GetUserFontSet()) {

--- a/layout/style/nsCSSRuleProcessor.cpp
+++ b/layout/style/nsCSSRuleProcessor.cpp
@@ -56,22 +56,16 @@
 #include "RuleProcessorCache.h"
 #include "nsIDOMMutationEvent.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
 
 typedef ArenaAllocator<4096, 8> CascadeAllocator;
 
-static nsTArray< RefPtr<nsAtom> >* sSystemMetrics = 0;
-
-#ifdef XP_WIN
-uint8_t nsCSSRuleProcessor::sWinThemeId = LookAndFeel::eWindowsTheme_Generic;
-#endif
-
 /**
  * A struct representing a given CSS rule and a particular selector
  * from that rule's selector list.
  */
 struct RuleSelectorPair {
   RuleSelectorPair(css::StyleRule* aRule, nsCSSSelector* aSelector)
     : mRule(aRule), mSelector(aSelector) {}
   // If this class ever grows a destructor, deal with
@@ -1042,199 +1036,16 @@ void
 nsCSSRuleProcessor::ClearSheets()
 {
   for (sheet_array_type::size_type i = mSheets.Length(); i-- != 0; ) {
     mSheets[i]->DropRuleProcessor(this);
   }
   mSheets.Clear();
 }
 
-/* static */ void
-nsCSSRuleProcessor::InitSystemMetrics()
-{
-  if (sSystemMetrics)
-    return;
-
-  MOZ_ASSERT(NS_IsMainThread());
-
-  sSystemMetrics = new nsTArray< RefPtr<nsAtom> >;
-
-  /***************************************************************************
-   * ANY METRICS ADDED HERE SHOULD ALSO BE ADDED AS MEDIA QUERIES IN         *
-   * nsMediaFeatures.cpp                                                     *
-   ***************************************************************************/
-
-  int32_t metricResult =
-    LookAndFeel::GetInt(LookAndFeel::eIntID_ScrollArrowStyle);
-  if (metricResult & LookAndFeel::eScrollArrow_StartBackward) {
-    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_start_backward);
-  }
-  if (metricResult & LookAndFeel::eScrollArrow_StartForward) {
-    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_start_forward);
-  }
-  if (metricResult & LookAndFeel::eScrollArrow_EndBackward) {
-    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_end_backward);
-  }
-  if (metricResult & LookAndFeel::eScrollArrow_EndForward) {
-    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_end_forward);
-  }
-
-  metricResult =
-    LookAndFeel::GetInt(LookAndFeel::eIntID_ScrollSliderStyle);
-  if (metricResult != LookAndFeel::eScrollThumbStyle_Normal) {
-    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_thumb_proportional);
-  }
-
-  metricResult =
-    LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars);
-  if (metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::overlay_scrollbars);
-  }
-
-  metricResult =
-    LookAndFeel::GetInt(LookAndFeel::eIntID_MenuBarDrag);
-  if (metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::menubar_drag);
-  }
-
-  nsresult rv =
-    LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsDefaultTheme, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::windows_default_theme);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_MacGraphiteTheme, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::mac_graphite_theme);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_MacYosemiteTheme, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::mac_yosemite_theme);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsAccentColorInTitlebar, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::windows_accent_color_in_titlebar);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_DWMCompositor, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::windows_compositor);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsGlass, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::windows_glass);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsClassic, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::windows_classic);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_TouchEnabled, &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::touch_enabled);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_SwipeAnimationEnabled,
-                           &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::swipe_animation_enabled);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDAvailable,
-                           &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_available);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDMinimizeButton,
-                           &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_minimize_button);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDMaximizeButton,
-                           &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_maximize_button);
-  }
-
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDCloseButton,
-                           &metricResult);
-  if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_close_button);
-  }
-
-#ifdef XP_WIN
-  if (NS_SUCCEEDED(
-        LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsThemeIdentifier,
-                            &metricResult))) {
-    nsCSSRuleProcessor::SetWindowsThemeIdentifier(static_cast<uint8_t>(metricResult));
-    switch(metricResult) {
-      case LookAndFeel::eWindowsTheme_Aero:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_aero);
-        break;
-      case LookAndFeel::eWindowsTheme_AeroLite:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_aero_lite);
-        break;
-      case LookAndFeel::eWindowsTheme_LunaBlue:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_luna_blue);
-        break;
-      case LookAndFeel::eWindowsTheme_LunaOlive:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_luna_olive);
-        break;
-      case LookAndFeel::eWindowsTheme_LunaSilver:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_luna_silver);
-        break;
-      case LookAndFeel::eWindowsTheme_Royale:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_royale);
-        break;
-      case LookAndFeel::eWindowsTheme_Zune:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_zune);
-        break;
-      case LookAndFeel::eWindowsTheme_Generic:
-        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_generic);
-        break;
-    }
-  }
-#endif
-}
-
-/* static */ void
-nsCSSRuleProcessor::FreeSystemMetrics()
-{
-  delete sSystemMetrics;
-  sSystemMetrics = nullptr;
-}
-
-/* static */ void
-nsCSSRuleProcessor::Shutdown()
-{
-  FreeSystemMetrics();
-}
-
-/* static */ bool
-nsCSSRuleProcessor::HasSystemMetric(nsAtom* aMetric)
-{
-  nsCSSRuleProcessor::InitSystemMetrics();
-  return sSystemMetrics->IndexOf(aMetric) != sSystemMetrics->NoIndex;
-}
-
-#ifdef XP_WIN
-/* static */ uint8_t
-nsCSSRuleProcessor::GetWindowsThemeIdentifier()
-{
-  nsCSSRuleProcessor::InitSystemMetrics();
-  return sWinThemeId;
-}
-#endif
-
 /* static */
 EventStates
 nsCSSRuleProcessor::GetContentState(const Element* aElement,
                                     bool aUsingPrivateBrowsing)
 {
   EventStates state = aElement->StyleState();
 
   // If we are not supposed to mark visited links as such, be sure to

--- a/layout/style/nsCSSRuleProcessor.h
+++ b/layout/style/nsCSSRuleProcessor.h
@@ -76,21 +76,16 @@ public:
                      bool aIsShared = false);
 
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
   NS_DECL_CYCLE_COLLECTION_CLASS(nsCSSRuleProcessor)
 
 public:
   nsresult ClearRuleCascades();
 
-  static void InitSystemMetrics();
-  static void Shutdown();
-  static void FreeSystemMetrics();
-  static bool HasSystemMetric(nsAtom* aMetric);
-
   /*
    * Returns true if the given aElement matches one of the
    * selectors in aSelectorList.  Note that this method will assume
    * the given aElement is not a relevant link.  aSelectorList must not
    * include any pseudo-element selectors.  aSelectorList is allowed
    * to be null; in this case false will be returned.
    */
   static bool SelectorListMatches(mozilla::dom::Element* aElement,
@@ -240,24 +235,16 @@ public:
   void ReleaseStyleSetRef();
   void SetInRuleProcessorCache(bool aVal) {
     MOZ_ASSERT(mIsShared);
     mInRuleProcessorCache = aVal;
   }
   bool IsInRuleProcessorCache() const { return mInRuleProcessorCache; }
   bool IsUsedByMultipleStyleSets() const { return mStyleSetRefCnt > 1; }
 
-#ifdef XP_WIN
-  // Cached theme identifier for the moz-windows-theme media query.
-  static uint8_t GetWindowsThemeIdentifier();
-  static void SetWindowsThemeIdentifier(uint8_t aId) {
-    sWinThemeId = aId;
-  }
-#endif
-
   struct StateSelector {
     StateSelector(mozilla::EventStates aStates, nsCSSSelector* aSelector)
       : mStates(aStates),
         mSelector(aSelector)
     {}
 
     mozilla::EventStates mStates;
     nsCSSSelector* mSelector;
@@ -315,15 +302,11 @@ private:
   // RefreshRuleCascade for why.
   bool mMustGatherDocumentRules;
 
   bool mInRuleProcessorCache;
 
 #ifdef DEBUG
   bool mDocumentRulesAndCacheKeyValid;
 #endif
-
-#ifdef XP_WIN
-  static uint8_t sWinThemeId;
-#endif
 };
 
 #endif /* nsCSSRuleProcessor_h_ */

--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
@@ -22,16 +22,23 @@
 #include "nsIDocument.h"
 #include "nsIWidget.h"
 #include "nsContentUtils.h"
 #include "mozilla/StyleSheet.h"
 #include "mozilla/StyleSheetInlines.h"
 
 using namespace mozilla;
 
+static nsTArray<RefPtr<nsAtom>>* sSystemMetrics = nullptr;
+
+#ifdef XP_WIN
+// Cached theme identifier for the moz-windows-theme media query.
+static uint8_t sWinThemeId = LookAndFeel::eWindowsTheme_Generic;
+#endif
+
 static const nsCSSProps::KTableEntry kOrientationKeywords[] = {
   { eCSSKeyword_portrait,                 NS_STYLE_ORIENTATION_PORTRAIT },
   { eCSSKeyword_landscape,                NS_STYLE_ORIENTATION_LANDSCAPE },
   { eCSSKeyword_UNKNOWN,                  -1 }
 };
 
 static const nsCSSProps::KTableEntry kScanKeywords[] = {
   { eCSSKeyword_progressive,              NS_STYLE_SCAN_PROGRESSIVE },
@@ -380,16 +387,32 @@ GetDevicePixelRatio(nsPresContext* aPres
 static void
 GetTransform3d(nsPresContext* aPresContext, const nsMediaFeature*,
                nsCSSValue& aResult)
 {
   // Gecko supports 3d transforms, so this feature is always 1.
   aResult.SetIntValue(1, eCSSUnit_Integer);
 }
 
+static bool
+HasSystemMetric(nsAtom* aMetric)
+{
+  nsMediaFeatures::InitSystemMetrics();
+  return sSystemMetrics->IndexOf(aMetric) != sSystemMetrics->NoIndex;
+}
+
+#ifdef XP_WIN
+static uint8_t
+GetWindowsThemeIdentifier()
+{
+  nsMediaFeatures::InitSystemMetrics();
+  return sWinThemeId;
+}
+#endif
+
 static void
 GetSystemMetric(nsPresContext* aPresContext, const nsMediaFeature* aFeature,
                 nsCSSValue& aResult)
 {
   aResult.Reset();
 
   const bool isAccessibleFromContentPages =
     !(aFeature->mReqFlags & nsMediaFeature::eUserAgentAndChromeOnly);
@@ -404,34 +427,33 @@ GetSystemMetric(nsPresContext* aPresCont
     // returned.)
     return;
   }
 
   MOZ_ASSERT(aFeature->mValueType == nsMediaFeature::eBoolInteger,
              "unexpected type");
 
   nsAtom* metricAtom = *aFeature->mData.mMetric;
-  bool hasMetric = nsCSSRuleProcessor::HasSystemMetric(metricAtom);
+  bool hasMetric = HasSystemMetric(metricAtom);
   aResult.SetIntValue(hasMetric ? 1 : 0, eCSSUnit_Integer);
 }
 
 static void
 GetWindowsTheme(nsPresContext* aPresContext, const nsMediaFeature* aFeature,
                 nsCSSValue& aResult)
 {
   aResult.Reset();
 
   MOZ_ASSERT(aFeature->mReqFlags & nsMediaFeature::eUserAgentAndChromeOnly);
   if (ShouldResistFingerprinting(aPresContext)) {
     return;
   }
 
 #ifdef XP_WIN
-  uint8_t windowsThemeId =
-    nsCSSRuleProcessor::GetWindowsThemeIdentifier();
+  uint8_t windowsThemeId = GetWindowsThemeIdentifier();
 
   // Classic mode should fail to match.
   if (windowsThemeId == LookAndFeel::eWindowsTheme_Classic)
     return;
 
   // Look up the appropriate theme string
   for (size_t i = 0; i < ArrayLength(themeStrings); ++i) {
     if (windowsThemeId == themeStrings[i].id) {
@@ -473,16 +495,182 @@ GetOperatingSystemVersion(nsPresContext*
 static void
 GetIsGlyph(nsPresContext* aPresContext, const nsMediaFeature* aFeature,
           nsCSSValue& aResult)
 {
   MOZ_ASSERT(aFeature->mReqFlags & nsMediaFeature::eUserAgentAndChromeOnly);
   aResult.SetIntValue(aPresContext->IsGlyph() ? 1 : 0, eCSSUnit_Integer);
 }
 
+/* static */ void
+nsMediaFeatures::InitSystemMetrics()
+{
+  if (sSystemMetrics)
+    return;
+
+  MOZ_ASSERT(NS_IsMainThread());
+
+  sSystemMetrics = new nsTArray<RefPtr<nsAtom>>;
+
+  /***************************************************************************
+   * ANY METRICS ADDED HERE SHOULD ALSO BE ADDED AS MEDIA QUERIES BELOW      *
+   ***************************************************************************/
+
+  int32_t metricResult =
+    LookAndFeel::GetInt(LookAndFeel::eIntID_ScrollArrowStyle);
+  if (metricResult & LookAndFeel::eScrollArrow_StartBackward) {
+    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_start_backward);
+  }
+  if (metricResult & LookAndFeel::eScrollArrow_StartForward) {
+    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_start_forward);
+  }
+  if (metricResult & LookAndFeel::eScrollArrow_EndBackward) {
+    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_end_backward);
+  }
+  if (metricResult & LookAndFeel::eScrollArrow_EndForward) {
+    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_end_forward);
+  }
+
+  metricResult =
+    LookAndFeel::GetInt(LookAndFeel::eIntID_ScrollSliderStyle);
+  if (metricResult != LookAndFeel::eScrollThumbStyle_Normal) {
+    sSystemMetrics->AppendElement(nsGkAtoms::scrollbar_thumb_proportional);
+  }
+
+  metricResult =
+    LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars);
+  if (metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::overlay_scrollbars);
+  }
+
+  metricResult =
+    LookAndFeel::GetInt(LookAndFeel::eIntID_MenuBarDrag);
+  if (metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::menubar_drag);
+  }
+
+  nsresult rv =
+    LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsDefaultTheme, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::windows_default_theme);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_MacGraphiteTheme, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::mac_graphite_theme);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_MacYosemiteTheme, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::mac_yosemite_theme);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsAccentColorInTitlebar, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::windows_accent_color_in_titlebar);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_DWMCompositor, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::windows_compositor);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsGlass, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::windows_glass);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsClassic, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::windows_classic);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_TouchEnabled, &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::touch_enabled);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_SwipeAnimationEnabled,
+                           &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::swipe_animation_enabled);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDAvailable,
+                           &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_available);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDMinimizeButton,
+                           &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_minimize_button);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDMaximizeButton,
+                           &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_maximize_button);
+  }
+
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_GTKCSDCloseButton,
+                           &metricResult);
+  if (NS_SUCCEEDED(rv) && metricResult) {
+    sSystemMetrics->AppendElement(nsGkAtoms::gtk_csd_close_button);
+  }
+
+#ifdef XP_WIN
+  if (NS_SUCCEEDED(
+        LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsThemeIdentifier,
+                            &metricResult))) {
+    sWinThemeId = metricResult;
+    switch (metricResult) {
+      case LookAndFeel::eWindowsTheme_Aero:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_aero);
+        break;
+      case LookAndFeel::eWindowsTheme_AeroLite:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_aero_lite);
+        break;
+      case LookAndFeel::eWindowsTheme_LunaBlue:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_luna_blue);
+        break;
+      case LookAndFeel::eWindowsTheme_LunaOlive:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_luna_olive);
+        break;
+      case LookAndFeel::eWindowsTheme_LunaSilver:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_luna_silver);
+        break;
+      case LookAndFeel::eWindowsTheme_Royale:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_royale);
+        break;
+      case LookAndFeel::eWindowsTheme_Zune:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_zune);
+        break;
+      case LookAndFeel::eWindowsTheme_Generic:
+        sSystemMetrics->AppendElement(nsGkAtoms::windows_theme_generic);
+        break;
+    }
+  }
+#endif
+}
+
+/* static */ void
+nsMediaFeatures::FreeSystemMetrics()
+{
+  delete sSystemMetrics;
+  sSystemMetrics = nullptr;
+}
+
+/* static */ void
+nsMediaFeatures::Shutdown()
+{
+  FreeSystemMetrics();
+}
+
 /*
  * Adding new media features requires (1) adding the new feature to this
  * array, with appropriate entries (and potentially any new code needed
  * to support new types in these entries and (2) ensuring that either
  * nsPresContext::MediaFeatureValuesChanged or
  * nsPresContext::PostMediaFeatureValuesChangedEvent is called when the
  * value that would be returned by the entry's mGetter changes.
  */

--- a/layout/style/nsMediaFeatures.h
+++ b/layout/style/nsMediaFeatures.h
@@ -80,13 +80,17 @@ struct nsMediaFeature
   // given presentation.  If it returns eCSSUnit_Null, the feature is
   // not present.
   nsMediaFeatureValueGetter mGetter;
 };
 
 class nsMediaFeatures
 {
 public:
+  static void InitSystemMetrics();
+  static void FreeSystemMetrics();
+  static void Shutdown();
+
   // Terminated with an entry whose mName is null.
   static const nsMediaFeature features[];
 };
 
 #endif /* !defined(nsMediaFeatures_h_) */