Issue #2828 - Part 5: Implement child rule processors

dom/animation/EffectCompositor.cpp

@@ -838,6 +838,12 @@ EffectCompositor::AnimationStyleRuleProcessor::MediumFeaturesChanged(
   return false;
 }
 
+nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>*
+EffectCompositor::AnimationStyleRuleProcessor::GetChildRuleProcessors()
+{
+  return nullptr;
+}
+
 void
 EffectCompositor::AnimationStyleRuleProcessor::RulesMatching(
   ElementRuleProcessorData* aData)

dom/animation/EffectCompositor.h

@@ -278,6 +278,8 @@ private:
                         AttributeRuleProcessorData* aData,
                         RestyleHintData& aRestyleHintDataResult) override;
     bool MediumFeaturesChanged(nsPresContext* aPresContext) override;
+    nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors()
+      override;
     void RulesMatching(ElementRuleProcessorData* aData) override;
     void RulesMatching(PseudoElementRuleProcessorData* aData) override;
     void RulesMatching(AnonBoxRuleProcessorData* aData) override;

layout/style/CascadeLayerRuleProcessor.cpp

@@ -0,0 +1,329 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/*
+ * style rule processor for cascade layers
+ */
+
+#include "nsAutoPtr.h"
+#include "nsCSSRuleProcessor.h"
+#include "nsRuleProcessorData.h"
+#include <algorithm>
+#include "nsIAtom.h"
+#include "PLDHashTable.h"
+#include "nsICSSPseudoComparator.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/css/StyleRule.h"
+#include "mozilla/css/GroupRule.h"
+#include "nsIDocument.h"
+#include "nsPresContext.h"
+#include "nsGkAtoms.h"
+#include "nsUnicharUtils.h"
+#include "nsError.h"
+#include "nsRuleWalker.h"
+#include "nsCSSPseudoClasses.h"
+#include "nsCSSPseudoElements.h"
+#include "nsIContent.h"
+#include "nsCOMPtr.h"
+#include "nsHashKeys.h"
+#include "nsStyleUtil.h"
+#include "nsQuickSort.h"
+#include "nsAttrValue.h"
+#include "nsAttrValueInlines.h"
+#include "nsAttrName.h"
+#include "nsTArray.h"
+#include "nsContentUtils.h"
+#include "nsIMediaList.h"
+#include "nsCSSRules.h"
+#include "nsStyleSet.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLSlotElement.h"
+#include "mozilla/dom/ShadowRoot.h"
+#include "nsNthIndexCache.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/EventStates.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/LookAndFeel.h"
+#include "mozilla/Likely.h"
+#include "mozilla/OperatorNewExtensions.h"
+#include "mozilla/TypedEnumBits.h"
+#include "RuleProcessorCache.h"
+#include "nsIDOMMutationEvent.h"
+#include "nsIMozBrowserFrame.h"
+#include "RuleCascadeData.h"
+#include "nsCSSRuleUtils.h"
+#include "CascadeLayerRuleProcessor.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// -------------------------------
+// Cascade layer style rule processor implementation
+//
+
+CascadeLayerRuleProcessor::CascadeLayerRuleProcessor(
+  CascadeEnumData* aLayer)
+  : mLayer(aLayer)
+  , mCascade(aLayer->mData)
+{
+  MOZ_ASSERT(mLayer,
+             "Layer rule processor must have an attached cascade layer");
+  MOZ_ASSERT(mCascade, "Cascade layer is missing its data");
+}
+
+/* virtual */ void
+CascadeLayerRuleProcessor::RulesMatching(ElementRuleProcessorData* aData)
+{
+  if (mCascade) {
+    mCascade->RulesMatching(aData);
+  }
+}
+
+/* virtual */ void
+CascadeLayerRuleProcessor::RulesMatching(
+  PseudoElementRuleProcessorData* aData)
+{
+  if (mCascade) {
+    mCascade->RulesMatching(aData);
+  }
+}
+
+/* virtual */ void
+CascadeLayerRuleProcessor::RulesMatching(AnonBoxRuleProcessorData* aData)
+{
+  if (mCascade) {
+    mCascade->RulesMatching(aData);
+  }
+}
+
+/* virtual */ void
+CascadeLayerRuleProcessor::RulesMatching(XULTreeRuleProcessorData* aData)
+{
+  if (mCascade) {
+    mCascade->RulesMatching(aData);
+  }
+}
+
+nsRestyleHint
+CascadeLayerRuleProcessor::HasStateDependentStyle(
+  ElementDependentRuleProcessorData* aData,
+  Element* aStatefulElement,
+  CSSPseudoElementType aPseudoType,
+  EventStates aStateMask,
+  nsRestyleHint& aHint)
+{
+  if (mCascade) {
+    mCascade->HasStateDependentStyle(
+      aData, aStatefulElement, aPseudoType, aStateMask, aHint);
+  }
+  return aHint;
+}
+
+nsRestyleHint
+CascadeLayerRuleProcessor::HasStateDependentStyle(
+  ElementDependentRuleProcessorData* aData,
+  Element* aStatefulElement,
+  CSSPseudoElementType aPseudoType,
+  EventStates aStateMask)
+{
+  nsRestyleHint hint = nsRestyleHint(0);
+  return HasStateDependentStyle(
+    aData, aStatefulElement, aPseudoType, aStateMask, hint);
+}
+
+/* virtual */ nsRestyleHint
+CascadeLayerRuleProcessor::HasStateDependentStyle(
+  StateRuleProcessorData* aData)
+{
+  return HasStateDependentStyle(
+    aData, aData->mElement, CSSPseudoElementType::NotPseudo, aData->mStateMask);
+}
+
+/* virtual */ nsRestyleHint
+CascadeLayerRuleProcessor::HasStateDependentStyle(
+  PseudoElementStateRuleProcessorData* aData)
+{
+  return HasStateDependentStyle(
+    aData, aData->mPseudoElement, aData->mPseudoType, aData->mStateMask);
+}
+
+/* virtual */ bool
+CascadeLayerRuleProcessor::HasDocumentStateDependentStyle(
+  StateRuleProcessorData* aData)
+{
+  if (mCascade && mCascade->mSelectorDocumentStates.HasAtLeastOneOfStates(
+        aData->mStateMask)) {
+    return true;
+  }
+
+  return false;
+}
+
+nsRestyleHint
+CascadeLayerRuleProcessor::HasAttributeDependentStyle(
+  AttributeRuleProcessorData* aData,
+  AttributeEnumData* aEnumData,
+  mozilla::RestyleHintData& aRestyleHintDataResult)
+{
+  // We could try making use of aData->mModType, but :not rules make it a bit
+  // of a pain to do so...  So just ignore it for now.
+
+  // Don't do our special handling of certain attributes if the attr
+  // hasn't changed yet.
+  if (aData->mAttrHasChanged) {
+    // check for the lwtheme and lwthemetextcolor attribute on root XUL elements
+    if ((aData->mAttribute == nsGkAtoms::lwtheme ||
+         aData->mAttribute == nsGkAtoms::lwthemetextcolor) &&
+        aData->mElement->GetNameSpaceID() == kNameSpaceID_XUL &&
+        aData->mElement == aData->mElement->OwnerDoc()->GetRootElement()) {
+      aEnumData->change = nsRestyleHint(aEnumData->change | eRestyle_Subtree);
+    }
+
+    // We don't know the namespace of the attribute, and xml:lang applies to
+    // all elements.  If the lang attribute changes, we need to restyle our
+    // whole subtree, since the :lang selector on our descendants can examine
+    // our lang attribute.
+    if (aData->mAttribute == nsGkAtoms::lang) {
+      aEnumData->change = nsRestyleHint(aEnumData->change | eRestyle_Subtree);
+    }
+  }
+  if (mCascade) {
+    mCascade->HasAttributeDependentStyle(aData, aEnumData, aRestyleHintDataResult);
+  }
+  return aEnumData->change;
+}
+
+/* virtual */ nsRestyleHint
+CascadeLayerRuleProcessor::HasAttributeDependentStyle(
+  AttributeRuleProcessorData* aData,
+  mozilla::RestyleHintData& aRestyleHintDataResult)
+{
+  AttributeEnumData data(aData, aRestyleHintDataResult);
+  return HasAttributeDependentStyle(aData, &data, aRestyleHintDataResult);
+}
+
+/* virtual */ bool
+CascadeLayerRuleProcessor::MediumFeaturesChanged(nsPresContext* aPresContext)
+{
+  // This is handled by our parent rule processor, so we don't need to do
+  // anything here.
+  return false;
+}
+
+/* virtual */ nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>*
+CascadeLayerRuleProcessor::GetChildRuleProcessors()
+{
+  return nullptr;
+}
+
+/* virtual */ size_t
+CascadeLayerRuleProcessor::SizeOfExcludingThis(
+  mozilla::MallocSizeOf aMallocSizeOf) const
+{
+  size_t n = 0;
+  n += mCascade->SizeOfIncludingThis(aMallocSizeOf);
+  // FIXME: size of attached cascade layer is not included.
+
+  return n;
+}
+
+/* virtual */ size_t
+CascadeLayerRuleProcessor::SizeOfIncludingThis(
+  mozilla::MallocSizeOf aMallocSizeOf) const
+{
+  return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+}
+
+nsCSSKeyframesRule*
+CascadeLayerRuleProcessor::KeyframesRuleForName(nsPresContext* aPresContext,
+                                                const nsString& aName)
+{
+  if (mCascade) {
+    return mCascade->mKeyframesRuleTable.Get(aName);
+  }
+
+  return nullptr;
+}
+
+nsCSSCounterStyleRule*
+CascadeLayerRuleProcessor::CounterStyleRuleForName(
+  nsPresContext* aPresContext,
+  const nsAString& aName)
+{
+  if (mCascade) {
+    return mCascade->mCounterStyleRuleTable.Get(aName);
+  }
+
+  return nullptr;
+}
+
+// Append all the currently-active font face rules to aArray.  Return
+// true for success and false for failure.
+bool
+CascadeLayerRuleProcessor::AppendFontFaceRules(
+  nsPresContext* aPresContext,
+  nsTArray<nsFontFaceRuleContainer>& aArray)
+{
+  if (mCascade) {
+    if (!aArray.AppendElements(mCascade->mFontFaceRules)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Append all the currently-active page rules to aArray.  Return
+// true for success and false for failure.
+bool
+CascadeLayerRuleProcessor::AppendPageRules(nsPresContext* aPresContext,
+                                             nsTArray<nsCSSPageRule*>& aArray)
+{
+  if (mCascade) {
+    if (!aArray.AppendElements(mCascade->mPageRules)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool
+CascadeLayerRuleProcessor::AppendFontFeatureValuesRules(
+  nsPresContext* aPresContext,
+  nsTArray<nsCSSFontFeatureValuesRule*>& aArray)
+{
+  if (mCascade) {
+    if (!aArray.AppendElements(mCascade->mFontFeatureValuesRules)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+CascadeLayerRuleProcessor::~CascadeLayerRuleProcessor()
+{
+  mCascade = nullptr;
+  if (mLayer) {
+    delete mLayer;
+  }
+  mLayer = nullptr;
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(CascadeLayerRuleProcessor)
+  NS_INTERFACE_MAP_ENTRY(nsIStyleRuleProcessor)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(CascadeLayerRuleProcessor)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(CascadeLayerRuleProcessor)
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(CascadeLayerRuleProcessor)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(CascadeLayerRuleProcessor)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(CascadeLayerRuleProcessor)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

layout/style/CascadeLayerRuleProcessor.h

@@ -0,0 +1,138 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+/*
+ * style rule processor for cascade layers
+ */
+
+#ifndef CascadeLayerRuleProcessor_h_
+#define CascadeLayerRuleProcessor_h_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/EventStates.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefCountType.h"
+#include "mozilla/SheetType.h"
+#include "mozilla/UniquePtr.h"
+#include "nsExpirationTracker.h"
+#include "nsIMediaList.h"
+#include "nsIStyleRuleProcessor.h"
+#include "nsRuleWalker.h"
+#include "nsTArray.h"
+
+struct AttributeEnumData;
+struct CascadeEnumData;
+struct RuleCascadeData;
+struct ElementDependentRuleProcessorData;
+struct nsFontFaceRuleContainer;
+struct ResolvedRuleCascades;
+class nsCSSKeyframesRule;
+class nsCSSPageRule;
+class nsCSSFontFeatureValuesRule;
+class nsCSSCounterStyleRule;
+
+namespace mozilla {
+class CSSStyleSheet;
+enum class CSSPseudoElementType : uint8_t;
+namespace css {
+class DocumentRule;
+} // namespace css
+} // namespace mozilla
+
+/**
+ * The cascade layer rule processor handles rules collected by the CSS style
+ * rule processor within the context of a specific cascade layer. It ensures
+ * rules are applied in the correct order, as defined by the CSS specification.
+ *
+ * It also handles unlayered rules, which are treated as belonging to an
+ * implicit base layer.
+ */
+ 
+class CascadeLayerRuleProcessor : public nsIStyleRuleProcessor
+{
+public:
+  CascadeLayerRuleProcessor(CascadeEnumData* aLayer);
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS(CascadeLayerRuleProcessor)
+
+public:
+  // nsIStyleRuleProcessor
+  virtual void RulesMatching(ElementRuleProcessorData* aData) override;
+
+  virtual void RulesMatching(PseudoElementRuleProcessorData* aData) override;
+
+  virtual void RulesMatching(AnonBoxRuleProcessorData* aData) override;
+
+  virtual void RulesMatching(XULTreeRuleProcessorData* aData) override;
+
+  virtual nsRestyleHint HasStateDependentStyle(
+    StateRuleProcessorData* aData) override;
+  virtual nsRestyleHint HasStateDependentStyle(
+    PseudoElementStateRuleProcessorData* aData) override;
+
+  virtual bool HasDocumentStateDependentStyle(
+    StateRuleProcessorData* aData) override;
+
+  virtual nsRestyleHint HasAttributeDependentStyle(
+    AttributeRuleProcessorData* aData,
+    mozilla::RestyleHintData& aRestyleHintDataResult) override;
+
+  virtual bool MediumFeaturesChanged(nsPresContext* aPresContext) override;
+
+  virtual nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors()
+    override;
+
+  virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const
+    MOZ_MUST_OVERRIDE override;
+  virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
+    MOZ_MUST_OVERRIDE override;
+
+  // The following API methods are consumed by nsStyleSet.
+
+  nsCSSKeyframesRule* KeyframesRuleForName(nsPresContext* aPresContext,
+                                           const nsString& aName);
+
+  nsCSSCounterStyleRule* CounterStyleRuleForName(nsPresContext* aPresContext,
+                                                 const nsAString& aName);
+
+  bool AppendFontFaceRules(nsPresContext* aPresContext,
+                           nsTArray<nsFontFaceRuleContainer>& aArray);
+
+  bool AppendPageRules(nsPresContext* aPresContext,
+                       nsTArray<nsCSSPageRule*>& aArray);
+
+  bool AppendFontFeatureValuesRules(
+    nsPresContext* aPresContext,
+    nsTArray<nsCSSFontFeatureValuesRule*>& aArray);
+
+  // The following API methods are consumed by nsCSSRuleProcessor only.
+  nsRestyleHint HasAttributeDependentStyle(
+    AttributeRuleProcessorData* aData,
+    AttributeEnumData* aEnumData,
+    mozilla::RestyleHintData& aRestyleHintDataResult);
+
+  nsRestyleHint HasStateDependentStyle(
+    ElementDependentRuleProcessorData* aData,
+    mozilla::dom::Element* aStatefulElement,
+    mozilla::CSSPseudoElementType aPseudoType,
+    mozilla::EventStates aStateMask,
+    nsRestyleHint& aHint);
+
+protected:
+  virtual ~CascadeLayerRuleProcessor();
+
+  CascadeEnumData* mLayer;
+  RuleCascadeData* mCascade;
+
+private:
+  nsRestyleHint HasStateDependentStyle(
+    ElementDependentRuleProcessorData* aData,
+    mozilla::dom::Element* aStatefulElement,
+    mozilla::CSSPseudoElementType aPseudoType,
+    mozilla::EventStates aStateMask);
+};
+
+#endif /* CascadeLayerRuleProcessor_h_ */

layout/style/RuleCascadeData.cpp

@@ -1188,6 +1188,13 @@ RuleCascadeData::HasAttributeDependentStyle(
   AttributeEnumData* aEnumData,
   mozilla::RestyleHintData& aRestyleHintDataResult)
 {
+  // Since we get both before and after notifications for attributes, we
+  // don't have to ignore aData->mAttribute while matching.  Just check
+  // whether we have selectors relevant to aData->mAttribute that we
+  // match.  If this is the before change notification, that will catch
+  // rules we might stop matching; if the after change notification, the
+  // ones we might have started matching.
+
   if (aData->mAttribute == nsGkAtoms::id) {
     nsIAtom* id = aData->mElement->GetID();
     if (id) {
@@ -1475,10 +1482,10 @@ size_t
 ResolvedRuleCascades::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
 {
   size_t n = aMallocSizeOf(this);
-  n += mOrderedData.ShallowSizeOfExcludingThis(aMallocSizeOf);
+  for (uint32_t i = 0; i < mProcessors.Length(); i++) {
-  for (RuleCascadeData* data : mOrderedData) {
+    n += mProcessors[i]->SizeOfIncludingThis(aMallocSizeOf);
-    n += data->SizeOfIncludingThis(aMallocSizeOf);
   }
+  n += mProcessors.ShallowSizeOfExcludingThis(aMallocSizeOf);
   return n;
 }
 
@@ -1553,7 +1560,6 @@ CascadeEnumData::CascadeEnumData(nsPresContext* aPresContext,
 #ifdef DEBUG
                                  CascadeEnumData* aParent,
 #endif
-                                 nsAutoPtr<ResolvedRuleCascades>& aContainer,
                                  bool aIsWeak,
                                  nsTArray<css::DocumentRule*>& aDocumentRules,
                                  nsDocumentRuleResultCacheKey& aDocumentKey,
@@ -1569,7 +1575,6 @@ CascadeEnumData::CascadeEnumData(nsPresContext* aPresContext,
   , mParent(aParent)
   , mIsRoot(false)
 #endif
-  , mContainer(aContainer)
   , mDocumentRules(aDocumentRules)
   , mDocumentCacheKey(aDocumentKey)
   , mSheetType(aSheetType)
@@ -1581,14 +1586,12 @@ CascadeEnumData::CascadeEnumData(nsPresContext* aPresContext,
 }
 
 CascadeEnumData::CascadeEnumData(nsPresContext* aPresContext,
-                                 nsAutoPtr<ResolvedRuleCascades>& aContainer,
                                  nsTArray<css::DocumentRule*>& aDocumentRules,
                                  nsDocumentRuleResultCacheKey& aDocumentKey,
                                  SheetType aSheetType,
                                  bool aMustGatherDocumentRules,
                                  nsMediaQueryResultCacheKey& aCacheKey)
   : mPresContext(aPresContext)
-  , mContainer(aContainer)
   , mIsAnonymous(false)
   , mIsWeak(false)
   , mWasFlattened(false)
@@ -1608,6 +1611,7 @@ CascadeEnumData::CascadeEnumData(nsPresContext* aPresContext,
 
 CascadeEnumData::~CascadeEnumData()
 {
+  delete mData;
   PL_FinishArenaPool(&mArena);
 }
 
@@ -1628,7 +1632,6 @@ CascadeEnumData::CreateNamedChildLayer(const nsTArray<nsString>& aPath)
 #ifdef DEBUG
                                      this,
 #endif
-                                     mContainer,
                                      false,
                                      mDocumentRules,
                                      mDocumentCacheKey,
@@ -1659,7 +1662,6 @@ CascadeEnumData::CreateAnonymousChildLayer()
 #ifdef DEBUG
                                                     this,
 #endif
-                                                    mContainer,
                                                     false,
                                                     mDocumentRules,
                                                     mDocumentCacheKey,
@@ -1751,7 +1753,7 @@ CascadeEnumData::AddRules()
 }
 
 void
-CascadeEnumData::Flatten()
+CascadeEnumData::EnumerateAllLayers(nsLayerEnumFunc aFunc, void* aData)
 {
   if (mWasFlattened) {
     return;
@@ -1759,16 +1761,15 @@ CascadeEnumData::Flatten()
 
   if (mPreLayers.Length() > 0) {
     for (CascadeEnumData* pre : mPreLayers) {
-      pre->Flatten();
+      pre->EnumerateAllLayers(aFunc, aData);
     }
   }
 
-  mContainer->mOrderedData.AppendElement(mData);
+  (*aFunc)(this, aData);
-  AddRules();
 
   if (mPostLayers.Length() > 0) {
     for (CascadeEnumData* post : mPostLayers) {
-      post->Flatten();
+      post->EnumerateAllLayers(aFunc, aData);
     }
   }
 

layout/style/RuleCascadeData.h

@@ -325,21 +325,17 @@ private:
 struct ResolvedRuleCascades
 {
   ResolvedRuleCascades(nsIAtom* aMedium)
-    : mUnlayered(nullptr)
+    : mCacheKey(aMedium)
-    , mCacheKey(aMedium)
     , mNext(nullptr)
   {
   }
 
   ~ResolvedRuleCascades()
   {
-    for (RuleCascadeData* data : mOrderedData) {
+    mProcessors.Clear();
-      delete data;
-    }
   }
 
-  nsTArray<RuleCascadeData*> mOrderedData;
+  nsTArray<nsCOMPtr<nsIStyleRuleProcessor>> mProcessors;
-  RuleCascadeData* mUnlayered;
   nsMediaQueryResultCacheKey mCacheKey;
   ResolvedRuleCascades* mNext; // for a different medium
 
@@ -353,7 +349,6 @@ struct CascadeEnumData
 #ifdef DEBUG
                   CascadeEnumData* aParent,
 #endif
-                  nsAutoPtr<ResolvedRuleCascades>& aContainer,
                   bool aIsWeak,
                   nsTArray<css::DocumentRule*>& aDocumentRules,
                   nsDocumentRuleResultCacheKey& aDocumentKey,
@@ -362,7 +357,6 @@ struct CascadeEnumData
                   nsMediaQueryResultCacheKey& aCacheKey);
 
   CascadeEnumData(nsPresContext* aPresContext,
-                  nsAutoPtr<ResolvedRuleCascades>& aContainer,
                   nsTArray<css::DocumentRule*>& aDocumentRules,
                   nsDocumentRuleResultCacheKey& aDocumentKey,
                   SheetType aSheetType,
@@ -395,18 +389,19 @@ struct CascadeEnumData
   CascadeEnumData* mParent;
   bool mIsRoot;
 #endif
-  nsAutoPtr<ResolvedRuleCascades>& mContainer;
   nsTArray<CascadeEnumData*> mPreLayers;
   nsTArray<CascadeEnumData*> mPostLayers;
   nsDataHashtable<nsStringHashKey, CascadeEnumData*> mLayers;
 
   CascadeEnumData* CreateNamedChildLayer(const nsTArray<nsString>& aPath);
   CascadeEnumData* CreateAnonymousChildLayer();
-  void Flatten();
+
+  typedef void (*nsLayerEnumFunc)(CascadeEnumData* aLayer, void* aData);
+  void EnumerateAllLayers(nsLayerEnumFunc aFunc, void* aData);
+  void AddRules();
 
 private:
   void Initialize();
-  void AddRules();
 
   static const PLDHashTableOps sRulesByWeightOps;
 };

layout/style/SVGAttrAnimationRuleProcessor.cpp

@@ -75,6 +75,12 @@ SVGAttrAnimationRuleProcessor::MediumFeaturesChanged(nsPresContext* aPresContext
   return false;
 }
 
+/* virtual */ nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>*
+SVGAttrAnimationRuleProcessor::GetChildRuleProcessors()
+{
+  return nullptr;
+}
+
 /* virtual */ void
 SVGAttrAnimationRuleProcessor::RulesMatching(PseudoElementRuleProcessorData* aData)
 {

layout/style/SVGAttrAnimationRuleProcessor.h

@@ -47,6 +47,8 @@ public:
     HasAttributeDependentStyle(AttributeRuleProcessorData* aData,
                                RestyleHintData& aRestyleHintDataResult) override;
   virtual bool MediumFeaturesChanged(nsPresContext* aPresContext) override;
+  virtual nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors()
+    override;
   virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
     const MOZ_MUST_OVERRIDE override;
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)

layout/style/moz.build

@@ -24,6 +24,7 @@ TEST_DIRS += ['test']
 EXPORTS += [
     '!nsStyleStructList.h',
     'AnimationCommon.h',
+    'CascadeLayerRuleProcessor.h',
     'CounterStyleManager.h',
     'nsAnimationManager.h',
     'nsComputedDOMStylePropertyList.h',
@@ -121,6 +122,7 @@ EXPORTS.mozilla.css += [
 UNIFIED_SOURCES += [
     'AnimationCollection.cpp',
     'AnimationCommon.cpp',
+    'CascadeLayerRuleProcessor.cpp',
     'CounterStyleManager.cpp',
     'CSS.cpp',
     'CSSLexer.cpp',

layout/style/nsCSSRuleProcessor.cpp

@@ -55,6 +55,7 @@
 #include "nsIMozBrowserFrame.h"
 #include "RuleCascadeData.h"
 #include "nsCSSRuleUtils.h"
+#include "CascadeLayerRuleProcessor.h"
 
 using namespace mozilla;
 using namespace mozilla::dom;
@@ -146,39 +147,30 @@ nsCSSRuleProcessor::ClearSheets()
 /* virtual */ void
 nsCSSRuleProcessor::RulesMatching(ElementRuleProcessorData *aData)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (!resolvedCascade) {
+      processor->RulesMatching(aData);
-    return;
     }
-  for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
-    cascade->RulesMatching(aData);
   }
 }
 
 /* virtual */ void
 nsCSSRuleProcessor::RulesMatching(PseudoElementRuleProcessorData* aData)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (!resolvedCascade) {
+      processor->RulesMatching(aData);
-    return;
     }
-  for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
-    cascade->RulesMatching(aData);
   }
 }
 
 /* virtual */ void
 nsCSSRuleProcessor::RulesMatching(AnonBoxRuleProcessorData* aData)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (!resolvedCascade) {
+      processor->RulesMatching(aData);
-    return;
     }
-  for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
-    cascade->RulesMatching(aData);
   }
 }
 
@@ -186,13 +178,10 @@ nsCSSRuleProcessor::RulesMatching(AnonBoxRuleProcessorData* aData)
 /* virtual */ void
 nsCSSRuleProcessor::RulesMatching(XULTreeRuleProcessorData* aData)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (!resolvedCascade) {
+      processor->RulesMatching(aData);
-    return;
     }
-  for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
-    cascade->RulesMatching(aData);
   }
 }
 #endif
@@ -207,19 +196,19 @@ nsCSSRuleProcessor::HasStateDependentStyle(ElementDependentRuleProcessorData* aD
              "mCurrentStyleScope will need to be saved and restored after the "
              "SelectorMatchesTree call");
 
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
-
   nsRestyleHint hint = nsRestyleHint(0);
-  if (resolvedCascade) {
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-      cascade->HasStateDependentStyle(
+      CascadeLayerRuleProcessor* layerProcessor =
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
+      layerProcessor->HasStateDependentStyle(
         aData, aStatefulElement, aPseudoType, aStateMask, hint);
     }
   }
   return hint;
 }
 
-nsRestyleHint
+/* virtual */ nsRestyleHint
 nsCSSRuleProcessor::HasStateDependentStyle(StateRuleProcessorData* aData)
 {
   return HasStateDependentStyle(aData,
@@ -228,7 +217,7 @@ nsCSSRuleProcessor::HasStateDependentStyle(StateRuleProcessorData* aData)
                                 aData->mStateMask);
 }
 
-nsRestyleHint
+/* virtual */ nsRestyleHint
 nsCSSRuleProcessor::HasStateDependentStyle(PseudoElementStateRuleProcessorData* aData)
 {
   return HasStateDependentStyle(aData,
@@ -237,15 +226,12 @@ nsCSSRuleProcessor::HasStateDependentStyle(PseudoElementStateRuleProcessorData*
                                 aData->mStateMask);
 }
 
-bool
+/* virtual */ bool
 nsCSSRuleProcessor::HasDocumentStateDependentStyle(StateRuleProcessorData* aData)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (resolvedCascade) {
+      if (processor->HasDocumentStateDependentStyle(aData)) {
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
-      if (cascade->mSelectorDocumentStates.HasAtLeastOneOfStates(
-            aData->mStateMask)) {
         return true;
       }
     }
@@ -259,47 +245,15 @@ nsCSSRuleProcessor::HasAttributeDependentStyle(
     AttributeRuleProcessorData* aData,
     RestyleHintData& aRestyleHintDataResult)
 {
-  //  We could try making use of aData->mModType, but :not rules make it a bit
-  //  of a pain to do so...  So just ignore it for now.
-
   AttributeEnumData data(aData, aRestyleHintDataResult);
-
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aData->mPresContext)) {
-  // Don't do our special handling of certain attributes if the attr
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  // hasn't changed yet.
+      CascadeLayerRuleProcessor* layerProcessor =
-  if (aData->mAttrHasChanged) {
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
-    // check for the lwtheme and lwthemetextcolor attribute on root XUL elements
+      layerProcessor->HasAttributeDependentStyle(
-    if ((aData->mAttribute == nsGkAtoms::lwtheme ||
-         aData->mAttribute == nsGkAtoms::lwthemetextcolor) &&
-        aData->mElement->GetNameSpaceID() == kNameSpaceID_XUL &&
-        aData->mElement == aData->mElement->OwnerDoc()->GetRootElement())
-      {
-        data.change = nsRestyleHint(data.change | eRestyle_Subtree);
-      }
-
-    // We don't know the namespace of the attribute, and xml:lang applies to
-    // all elements.  If the lang attribute changes, we need to restyle our
-    // whole subtree, since the :lang selector on our descendants can examine
-    // our lang attribute.
-    if (aData->mAttribute == nsGkAtoms::lang) {
-      data.change = nsRestyleHint(data.change | eRestyle_Subtree);
-    }
-  }
-
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aData->mPresContext);
-
-  // Since we get both before and after notifications for attributes, we
-  // don't have to ignore aData->mAttribute while matching.  Just check
-  // whether we have selectors relevant to aData->mAttribute that we
-  // match.  If this is the before change notification, that will catch
-  // rules we might stop matching; if the after change notification, the
-  // ones we might have started matching.
-  if (resolvedCascade) {
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
-      cascade->HasAttributeDependentStyle(
         aData, &data, aRestyleHintDataResult);
     }
   }
-
   return data.change;
 }
 
@@ -341,13 +295,21 @@ nsCSSRuleProcessor::MediumFeaturesChanged(nsPresContext* aPresContext)
   return false;
 }
 
+/* virtual */ nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>*
+nsCSSRuleProcessor::GetChildRuleProcessors()
+{
+  return mRuleCascades
+    ? &mRuleCascades->mProcessors
+    : nullptr;
+}
+
 UniquePtr<nsMediaQueryResultCacheKey>
 nsCSSRuleProcessor::CloneMQCacheKey()
 {
   MOZ_ASSERT(!(mRuleCascades && mPreviousCacheKey));
 
   ResolvedRuleCascades* c = mRuleCascades;
-  if (!c || !c->mUnlayered) {
+  if (!c) {
     // We might have an mPreviousCacheKey.  It already comes from a call
     // to CloneMQCacheKey, so don't bother checking
     // HasFeatureConditions().
@@ -373,9 +335,9 @@ nsCSSRuleProcessor::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
 {
   size_t n = 0;
   n += mSheets.ShallowSizeOfExcludingThis(aMallocSizeOf);
-  for (ResolvedRuleCascades* cascade = mRuleCascades; cascade;
+  for (ResolvedRuleCascades* cascades = mRuleCascades; cascades;
-       cascade = cascade->mNext) {
+       cascades = cascades->mNext) {
-    n += cascade->SizeOfIncludingThis(aMallocSizeOf);
+    n += cascades->SizeOfIncludingThis(aMallocSizeOf);
   }
 
   return n;
@@ -387,18 +349,16 @@ nsCSSRuleProcessor::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
   return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
 }
 
-// Append all the currently-active font face rules to aArray.  Return
-// true for success and false for failure.
 bool
 nsCSSRuleProcessor::AppendFontFaceRules(
                               nsPresContext *aPresContext,
                               nsTArray<nsFontFaceRuleContainer>& aArray)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (resolvedCascade) {
+      CascadeLayerRuleProcessor* layerProcessor =
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
-      if (!aArray.AppendElements(cascade->mFontFaceRules)) {
+      if (!layerProcessor->AppendFontFaceRules(aPresContext, aArray)) {
         return false;
       }
     }
@@ -411,13 +371,14 @@ nsCSSKeyframesRule*
 nsCSSRuleProcessor::KeyframesRuleForName(nsPresContext* aPresContext,
                                          const nsString& aName)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aPresContext);
-
   nsCSSKeyframesRule* rule = nullptr;
-  if (resolvedCascade) {
+
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aPresContext)) {
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
+      CascadeLayerRuleProcessor* layerProcessor =
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
       if (nsCSSKeyframesRule* newRule =
-            cascade->mKeyframesRuleTable.Get(aName)) {
+            layerProcessor->KeyframesRuleForName(aPresContext, aName)) {
         rule = newRule;
       }
     }
@@ -430,13 +391,13 @@ nsCSSCounterStyleRule*
 nsCSSRuleProcessor::CounterStyleRuleForName(nsPresContext* aPresContext,
                                             const nsAString& aName)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aPresContext);
-
   nsCSSCounterStyleRule* rule = nullptr;
-  if (resolvedCascade) {
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aPresContext)) {
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
+      CascadeLayerRuleProcessor* layerProcessor =
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
       if (nsCSSCounterStyleRule* newRule =
-            cascade->mCounterStyleRuleTable.Get(aName)) {
+            layerProcessor->CounterStyleRuleForName(aPresContext, aName)) {
         rule = newRule;
       }
     }
@@ -445,18 +406,16 @@ nsCSSRuleProcessor::CounterStyleRuleForName(nsPresContext* aPresContext,
   return rule;
 }
 
-// Append all the currently-active page rules to aArray.  Return
-// true for success and false for failure.
 bool
 nsCSSRuleProcessor::AppendPageRules(
                               nsPresContext* aPresContext,
                               nsTArray<nsCSSPageRule*>& aArray)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (resolvedCascade) {
+      CascadeLayerRuleProcessor* layerProcessor =
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
-      if (!aArray.AppendElements(cascade->mPageRules)) {
+      if (!layerProcessor->AppendPageRules(aPresContext, aArray)) {
         return false;
       }
     }
@@ -470,11 +429,11 @@ nsCSSRuleProcessor::AppendFontFeatureValuesRules(
                               nsPresContext *aPresContext,
                               nsTArray<nsCSSFontFeatureValuesRule*>& aArray)
 {
-  ResolvedRuleCascades* resolvedCascade = GetRuleCascade(aPresContext);
+  if (ResolvedRuleCascades* cascades = GetRuleCascade(aPresContext)) {
-
+    for (nsCOMPtr<nsIStyleRuleProcessor> processor : cascades->mProcessors) {
-  if (resolvedCascade) {
+      CascadeLayerRuleProcessor* layerProcessor =
-    for (RuleCascadeData* cascade : resolvedCascade->mOrderedData) {
+        static_cast<CascadeLayerRuleProcessor*>(processor.get());
-      if (!aArray.AppendElements(cascade->mFontFeatureValuesRules)) {
+      if (!layerProcessor->AppendFontFeatureValuesRules(aPresContext, aArray)) {
         return false;
       }
     }
@@ -733,6 +692,19 @@ nsCSSRuleProcessor::GetRuleCascade(nsPresContext* aPresContext)
   return mRuleCascades;
 }
 
+/**
+ * This enumerates layers in a sheet and creates child rule processors
+ * for each layer. The child rule processors are created in the order
+ * that the layers are encountered.
+ */
+static void
+CreateChildProcessorsEnumFunc(CascadeEnumData* aLayer, void* aData)
+{
+  aLayer->AddRules();
+  ResolvedRuleCascades* data = static_cast<ResolvedRuleCascades*>(aData);
+  data->mProcessors.AppendElement(new CascadeLayerRuleProcessor(aLayer));
+}
+
 void
 nsCSSRuleProcessor::RefreshRuleCascade(nsPresContext* aPresContext)
 {
@@ -760,24 +732,26 @@ nsCSSRuleProcessor::RefreshRuleCascade(nsPresContext* aPresContext)
   mPreviousCacheKey = nullptr;
 
   if (mSheets.Length() != 0) {
-    nsAutoPtr<ResolvedRuleCascades> resolvedCascade(
+    nsAutoPtr<ResolvedRuleCascades> cascades(
       new ResolvedRuleCascades(aPresContext->Medium()));
-    CascadeEnumData unlayered(aPresContext,
+    CascadeEnumData* unlayered(new CascadeEnumData(aPresContext,
-                              resolvedCascade,
                                                    mDocumentRules,
                                                    mDocumentCacheKey,
                                                    mSheetType,
                                                    mMustGatherDocumentRules,
-                              resolvedCascade->mCacheKey);
+                                                   cascades->mCacheKey));
-    if (unlayered.mData) {
+    if (unlayered->mData) {
       for (uint32_t i = 0; i < mSheets.Length(); ++i) {
-        if (!CascadeSheet(mSheets.ElementAt(i), &unlayered)) {
+        if (!CascadeSheet(mSheets.ElementAt(i), unlayered)) {
           return; /* out of memory */
         }
       }
 
-      unlayered.Flatten();
+      // Ensure that the current one is always mRuleCascades.
-      resolvedCascade->mUnlayered = unlayered.mData;
+      cascades->mNext = mRuleCascades;
+      mRuleCascades = cascades.forget();
+
+      unlayered->EnumerateAllLayers(CreateChildProcessorsEnumFunc, mRuleCascades);
 
       // mMustGatherDocumentRules controls whether we build mDocumentRules
       // and mDocumentCacheKey so that they can be used as keys by the
@@ -812,10 +786,6 @@ nsCSSRuleProcessor::RefreshRuleCascade(nsPresContext* aPresContext)
         mDocumentRulesAndCacheKeyValid = true;
 #endif
       }
-
-      // Ensure that the current one is always mRuleCascades.
-      resolvedCascade->mNext = mRuleCascades;
-      mRuleCascades = resolvedCascade.forget();
     }
   }
   return;

layout/style/nsCSSRuleProcessor.h

@@ -99,6 +99,9 @@ public:
 
   virtual bool MediumFeaturesChanged(nsPresContext* aPresContext) override;
 
+  virtual nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors()
+    override;
+
   /**
    * If this rule processor currently has a substantive media query
    * result cache key, return a copy of it.

layout/style/nsHTMLCSSStyleSheet.cpp

@@ -162,6 +162,12 @@ nsHTMLCSSStyleSheet::MediumFeaturesChanged(nsPresContext* aPresContext)
   return false;
 }
 
+/* virtual */ nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>*
+nsHTMLCSSStyleSheet::GetChildRuleProcessors()
+{
+  return nullptr;
+}
+
 /* virtual */ size_t
 nsHTMLCSSStyleSheet::SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
 {

layout/style/nsHTMLCSSStyleSheet.h

@@ -47,6 +47,8 @@ public:
     HasAttributeDependentStyle(AttributeRuleProcessorData* aData,
                                mozilla::RestyleHintData& aRestyleHintDataResult) override;
   virtual bool MediumFeaturesChanged(nsPresContext* aPresContext) override;
+  virtual nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors()
+    override;
   virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
     const MOZ_MUST_OVERRIDE override;
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)

layout/style/nsHTMLStyleSheet.cpp

@@ -439,6 +439,12 @@ nsHTMLStyleSheet::MediumFeaturesChanged(nsPresContext* aPresContext)
   return false;
 }
 
+/* virtual */ nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>*
+nsHTMLStyleSheet::GetChildRuleProcessors()
+{
+  return nullptr;
+}
+
 /* virtual */ size_t
 nsHTMLStyleSheet::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
 {

layout/style/nsHTMLStyleSheet.h

@@ -47,6 +47,8 @@ public:
     HasAttributeDependentStyle(AttributeRuleProcessorData* aData,
                                mozilla::RestyleHintData& aRestyleHintDataResult) override;
   virtual bool MediumFeaturesChanged(nsPresContext* aPresContext) override;
+  virtual nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors()
+    override;
   virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf)
     const MOZ_MUST_OVERRIDE override;
   virtual size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf)

layout/style/nsIStyleRuleProcessor.h

@@ -126,6 +126,13 @@ public:
    */
   virtual bool MediumFeaturesChanged(nsPresContext* aPresContext) = 0;
 
+  /**
+   * Returns an array of style rule processors if this origin supports
+   * cascade layers. The array will contain the rule processors for each
+   * layer in the order in which they should be applied.
+   */
+  virtual nsTArray<nsCOMPtr<nsIStyleRuleProcessor>>* GetChildRuleProcessors() = 0;
+
   /**
    * Report the size of this style rule processor to about:memory.  A
    * processor may return 0.