Oilpan: Make the Node hierarchy RefCountedGarbageCollected instead of TreeShared.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 15f087205287c8e6d9258c13149744eb81a00a9c..2172488dc5ab65d4cd0f917477c045d3e73840b1 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -479,7 +479,7 @@ Document::Document(const DocumentInit& initializer, DocumentClassFlags documentC
     , m_animationClock(AnimationClock::create())
     , m_timeline(DocumentTimeline::create(this))
     , m_transitionTimeline(TransitionTimeline::create(this))
-    , m_templateDocumentHost(0)
+    , m_templateDocumentHost(nullptr)
     , m_didAssociateFormControlsTimer(this, &Document::didAssociateFormControlsTimerFired)
     , m_hasViewportUnits(false)
     , m_styleRecalcElementCounter(0)
@@ -534,14 +534,16 @@ Document::~Document()
     // When they die in the same GC round, the list of visibility observers
     // will not be empty on Document destruction.
     ASSERT(m_visibilityObservers.isEmpty());
-#endif
 
     if (m_templateDocument)
         m_templateDocument->m_templateDocumentHost = 0; // balanced in ensureTemplateDocument().
+#endif
 
     m_scriptRunner.clear();
 
+#if !ENABLE(OILPAN)
     removeAllEventListenersRecursively();
+#endif
 
     // Currently we believe that Document can never outlive the parser.
     // Although the Document may be replaced synchronously, DocumentParsers
@@ -568,11 +570,11 @@ Document::~Document()
     m_timeline->detachFromDocument();
     m_transitionTimeline->detachFromDocument();
 
+#if !ENABLE(OILPAN)
     // We need to destroy CSSFontSelector before destroying m_fetcher.
     if (m_styleEngine)
         m_styleEngine->detachFromDocument();
 
-#if !ENABLE(OILPAN)
     if (m_elemSheet)
         m_elemSheet->clearOwnerNode();
 #endif
@@ -600,7 +602,9 @@ Document::~Document()
 
 void Document::dispose()

[Mads Ager (chromium), 2014/05/05 10:18:36]

The Document::dispose method breaks a lot of reference cycles that would
otherwise leak. With Oilpan all of this reference cycle breaking is unnecessary.
The form controller is still cleared (it contains RefPtrs) but that should be
removed as well in a follow-up change.

 {
+#if !ENABLE(OILPAN)
     ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun);
+
     // We must make sure not to be retaining any of our children through
     // these extra pointers or we will create a reference cycle.
     m_docType = nullptr;
@@ -625,13 +629,18 @@ void Document::dispose()
     // removeDetachedChildren() doesn't always unregister IDs,
     // so tear down scope information upfront to avoid having stale references in the map.
     destroyTreeScopeData();
+
     removeDetachedChildren();
+#endif
+
     // removeDetachedChildren() can access FormController.
     m_formController.clear();
 
+#if !ENABLE(OILPAN)
     m_markers->clear();
 
     m_cssCanvasElements.clear();
+#endif
 
     // FIXME: consider using ActiveDOMObject.
     if (m_scriptedAnimationController)
@@ -641,7 +650,10 @@ void Document::dispose()
     if (svgExtensions())
         accessSVGExtensions().pauseAnimations();
 
+#if !ENABLE(OILPAN)
     m_lifecycle.advanceTo(DocumentLifecycle::Disposed);
+#endif
+
     lifecycleNotifier().notifyDocumentWasDisposed();
 }
 
@@ -1362,7 +1374,7 @@ void Document::setTitle(const String& title)
     else if (!m_titleElement) {
         if (HTMLElement* headElement = head()) {
             m_titleElement = HTMLTitleElement::create(*this);
-            headElement->appendChild(m_titleElement);
+            headElement->appendChild(m_titleElement.get());
         }
     }
 
@@ -2223,6 +2235,9 @@ void Document::detach(const AttachContext& context)
 
     lifecycleNotifier().notifyDocumentWasDetached();
     m_lifecycle.advanceTo(DocumentLifecycle::Stopped);
+#if ENABLE(OILPAN)
+    dispose();
+#endif
 }
 
 void Document::prepareForDestruction()
@@ -3525,7 +3540,7 @@ bool Document::setFocusedElement(PassRefPtr<Element> prpNewFocusedElement, Focus
         return true;
 
     bool focusChangeBlocked = false;
-    RefPtr<Element> oldFocusedElement = m_focusedElement;
+    RefPtrWillBeRawPtr<Element> oldFocusedElement = m_focusedElement;
     m_focusedElement = nullptr;
 
     // Remove focus from the existing focus node (if any)
@@ -4878,7 +4893,7 @@ void Document::getCSSCanvasContext(const String& type, const String& name, int w
 
 HTMLCanvasElement& Document::getCSSCanvasElement(const String& name)
 {
-    RefPtr<HTMLCanvasElement>& element = m_cssCanvasElements.add(name, nullptr).storedValue->value;
+    RefPtrWillBeMember<HTMLCanvasElement>& element = m_cssCanvasElements.add(name, nullptr).storedValue->value;
     if (!element) {
         element = HTMLCanvasElement::create(*this);
         element->setAccelerationDisabled(true);
@@ -5663,10 +5678,28 @@ void Document::clearWeakMembers(Visitor* visitor)
 
 void Document::trace(Visitor* visitor)
 {
+    visitor->trace(m_docType);
+    visitor->trace(m_autofocusElement);
+    visitor->trace(m_focusedElement);
+    visitor->trace(m_hoverNode);
+    visitor->trace(m_activeHoverElement);
+    visitor->trace(m_documentElement);
+    visitor->trace(m_titleElement);
+    visitor->trace(m_currentScriptStack);
+    visitor->trace(m_transformSourceDocument);
+    visitor->trace(m_cssCanvasElements);
+    visitor->trace(m_topLayerElements);
+    visitor->trace(m_mediaQueryMatcher);
+    visitor->trace(m_elemSheet);
+    visitor->trace(m_styleEngine);
     visitor->trace(m_styleSheetList);
     visitor->trace(m_mediaQueryMatcher);
+    visitor->trace(m_associatedFormControls);
+    visitor->trace(m_templateDocument);
+    visitor->trace(m_templateDocumentHost);
     visitor->trace(m_visibilityObservers);
     visitor->trace(m_contextFeatures);
+    visitor->trace(m_userActionElements);
     visitor->registerWeakMembers<Document, &Document::clearWeakMembers>(this);
     DocumentSupplementable::trace(visitor);
     TreeScope::trace(visitor);