Bug 1412145 - Drop more backpointers of CSSOM objects in dtor and unlink. r=bz

MozReview-Commit-ID: Ftg3WMBBNlO

layout/style/GroupRule.cpp

@@ -198,6 +198,13 @@ GeckoGroupRuleRules::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
 // ServoGroupRuleRules
 //
 
+ServoGroupRuleRules::~ServoGroupRuleRules()
+{
+  if (mRuleList) {
+    mRuleList->DropReference();
+  }
+}
+
 #ifdef DEBUG
 void
 ServoGroupRuleRules::List(FILE* out, int32_t aIndent) const

layout/style/GroupRule.h

@@ -87,6 +87,7 @@ struct ServoGroupRuleRules
     // Do we ever clone Servo rules?
     MOZ_ASSERT_UNREACHABLE("stylo: Cloning GroupRule not implemented");
   }
+  ~ServoGroupRuleRules();
 
   void SetParentRule(GroupRule* aParentRule) {
     if (mRuleList) {

layout/style/MediaList.h

@@ -84,7 +84,9 @@ protected:
   virtual nsresult Delete(const nsAString& aOldMedium) = 0;
   virtual nsresult Append(const nsAString& aNewMedium) = 0;
 
-  virtual ~MediaList() {}
+  virtual ~MediaList() {
+    MOZ_ASSERT(!mStyleSheet, "Backpointer should have been cleared");
+  }
 
   // not refcounted; sheet will let us know when it goes away
   // mStyleSheet is the sheet that needs to be dirtied when this

layout/style/ServoCSSRuleList.cpp

@@ -234,6 +234,8 @@ ServoCSSRuleList::GetDOMCSSRuleType(uint32_t aIndex) const
 
 ServoCSSRuleList::~ServoCSSRuleList()
 {
+  MOZ_ASSERT(!mStyleSheet, "Backpointer should have been cleared");
+  MOZ_ASSERT(!mParentRule, "Backpointer should have been cleared");
   DropAllRules();
 }
 

layout/style/ServoKeyframeRule.cpp

@@ -35,7 +35,10 @@ public:
     return NS_OK;
   }
 
-  void DropReference() { mRule = nullptr; }
+  void DropReference() {
+    mRule = nullptr;
+    mDecls->SetOwningRule(nullptr);
+  }
 
   DeclarationBlock* GetCSSDeclaration(Operation aOperation) final
   {
@@ -83,7 +86,9 @@ public:
   }
 
 private:
-  virtual ~ServoKeyframeDeclaration() {}
+  virtual ~ServoKeyframeDeclaration() {
+    MOZ_ASSERT(!mRule, "Backpointer should have been cleared");
+  }
 
   ServoKeyframeRule* mRule;
   RefPtr<ServoDeclarationBlock> mDecls;
@@ -104,6 +109,9 @@ NS_INTERFACE_MAP_END_INHERITING(nsDOMCSSDeclaration)
 
 ServoKeyframeRule::~ServoKeyframeRule()
 {
+  if (mDeclaration) {
+    mDeclaration->DropReference();
+  }
 }
 
 NS_IMPL_ADDREF_INHERITED(ServoKeyframeRule, dom::CSSKeyframeRule)

layout/style/ServoKeyframesRule.cpp

@@ -90,7 +90,10 @@ public:
   {
     mStyleSheet = nullptr;
     mParentRule = nullptr;
-    DropAllRules();
+    for (css::Rule* rule : mRules) {
+      rule->SetStyleSheet(nullptr);
+      rule->SetParentRule(nullptr);
+    }
   }
 
   size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const
@@ -103,15 +106,16 @@ public:
   }
 
 private:
-  virtual ~ServoKeyframeList() {}
+  virtual ~ServoKeyframeList() {
+    MOZ_ASSERT(!mParentRule, "Backpointer should have been cleared");
+    MOZ_ASSERT(!mStyleSheet, "Backpointer should have been cleared");
+    DropAllRules();
+  }
 
   void DropAllRules()
   {
-    for (css::Rule* rule : mRules) {
-      if (rule) {
-        rule->SetStyleSheet(nullptr);
-        rule->SetParentRule(nullptr);
-      }
+    if (mParentRule || mStyleSheet) {
+      DropReference();
     }
     mRules.Clear();
     mRawRule = nullptr;
@@ -163,6 +167,9 @@ ServoKeyframesRule::ServoKeyframesRule(RefPtr<RawServoKeyframesRule> aRawRule,
 
 ServoKeyframesRule::~ServoKeyframesRule()
 {
+  if (mKeyframeList) {
+    mKeyframeList->DropReference();
+  }
 }
 
 NS_IMPL_ADDREF_INHERITED(ServoKeyframesRule, dom::CSSKeyframesRule)

layout/style/ServoMediaRule.cpp

@@ -24,6 +24,9 @@ ServoMediaRule::ServoMediaRule(RefPtr<RawServoMediaRule> aRawRule,
 
 ServoMediaRule::~ServoMediaRule()
 {
+  if (mMediaList) {
+    mMediaList->SetStyleSheet(nullptr);
+  }
 }
 
 NS_IMPL_ADDREF_INHERITED(ServoMediaRule, CSSMediaRule)
@@ -33,8 +36,18 @@ NS_IMPL_RELEASE_INHERITED(ServoMediaRule, CSSMediaRule)
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ServoMediaRule)
 NS_INTERFACE_MAP_END_INHERITING(CSSMediaRule)
 
-NS_IMPL_CYCLE_COLLECTION_INHERITED(ServoMediaRule, CSSMediaRule,
-                                   mMediaList)
+NS_IMPL_CYCLE_COLLECTION_CLASS(ServoMediaRule)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(ServoMediaRule, CSSMediaRule)
+  if (tmp->mMediaList) {
+    tmp->mMediaList->SetStyleSheet(nullptr);
+    tmp->mMediaList = nullptr;
+  }
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ServoMediaRule, CSSMediaRule)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMediaList)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 /* virtual */ already_AddRefed<css::Rule>
 ServoMediaRule::Clone() const

layout/style/ServoPageRule.cpp

@@ -26,6 +26,7 @@ ServoPageRuleDeclaration::ServoPageRuleDeclaration(
 
 ServoPageRuleDeclaration::~ServoPageRuleDeclaration()
 {
+  mDecls->SetOwningRule(nullptr);
 }
 
 // QueryInterface implementation for ServoPageRuleDeclaration
@@ -143,6 +144,7 @@ NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(ServoPageRule, CSSPageRule)
   // NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER which we can't use
   // directly because the wrapper is on the declaration, not on us.
   tmp->mDecls.ReleaseWrapper(static_cast<nsISupports*>(p));
+  tmp->mDecls.mDecls->SetOwningRule(nullptr);
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
 
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ServoPageRule, CSSPageRule)

layout/style/ServoStyleRule.cpp

@@ -28,6 +28,7 @@ ServoStyleRuleDeclaration::ServoStyleRuleDeclaration(
 
 ServoStyleRuleDeclaration::~ServoStyleRuleDeclaration()
 {
+  mDecls->SetOwningRule(nullptr);
 }
 
 // QueryInterface implementation for ServoStyleRuleDeclaration

layout/style/nsCSSRules.cpp

@@ -208,12 +208,25 @@ ImportRule::~ImportRule()
 NS_IMPL_ADDREF_INHERITED(ImportRule, CSSImportRule)
 NS_IMPL_RELEASE_INHERITED(ImportRule, CSSImportRule)
 
-NS_IMPL_CYCLE_COLLECTION_INHERITED(ImportRule, CSSImportRule, mMedia, mChildSheet)
-
 // QueryInterface implementation for ImportRule
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ImportRule)
 NS_INTERFACE_MAP_END_INHERITING(CSSImportRule)
 
+NS_IMPL_CYCLE_COLLECTION_CLASS(ImportRule)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(ImportRule, CSSImportRule)
+  if (tmp->mChildSheet) {
+    tmp->mChildSheet->SetOwnerRule(nullptr);
+    tmp->mChildSheet = nullptr;
+  }
+  tmp->mMedia = nullptr;
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ImportRule, CSSImportRule)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMedia)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mChildSheet)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
 #ifdef DEBUG
 /* virtual */ void
 ImportRule::List(FILE* out, int32_t aIndent) const
@@ -338,8 +351,18 @@ NS_IMPL_RELEASE_INHERITED(MediaRule, CSSMediaRule)
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(MediaRule)
 NS_INTERFACE_MAP_END_INHERITING(CSSMediaRule)
 
-NS_IMPL_CYCLE_COLLECTION_INHERITED(MediaRule, CSSMediaRule,
-                                   mMedia)
+NS_IMPL_CYCLE_COLLECTION_CLASS(MediaRule)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(MediaRule, CSSMediaRule)
+  if (tmp->mMedia) {
+    tmp->mMedia->SetStyleSheet(nullptr);
+    tmp->mMedia = nullptr;
+  }
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(MediaRule, CSSMediaRule)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMedia)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
 
 /* virtual */ void
 MediaRule::SetStyleSheet(StyleSheet* aSheet)