Oilpan: move 2D Canvas and WebGL objects to the heap.

Source/core/html/canvas/WebGLContextGroup.h

Index: Source/core/html/canvas/WebGLContextGroup.h
diff --git a/Source/core/html/canvas/WebGLContextGroup.h b/Source/core/html/canvas/WebGLContextGroup.h
index 6c2f995354013332bda0e70ba332cefb2c2f7aec..e2d6fbf4f8d9e2dc3c99f98092ff9d2f579b9f27 100644
--- a/Source/core/html/canvas/WebGLContextGroup.h
+++ b/Source/core/html/canvas/WebGLContextGroup.h
@@ -27,6 +27,7 @@
 #define WebGLContextGroup_h
 
 #include "core/html/canvas/WebGLRenderingContextBase.h"
+#include "platform/heap/Handle.h"
 #include "wtf/HashSet.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
@@ -43,10 +44,10 @@ class WebGLRenderingContextBase;
 
 typedef int ExceptionCode;
 
-class WebGLContextGroup FINAL : public RefCounted<WebGLContextGroup> {
+class WebGLContextGroup FINAL : public RefCountedWillBeGarbageCollected<WebGLContextGroup> {
+    DECLARE_EMPTY_DESTRUCTOR_WILL_BE_REMOVED(WebGLContextGroup);
 public:
-    static PassRefPtr<WebGLContextGroup> create();
-    ~WebGLContextGroup();
+    static PassRefPtrWillBeRawPtr<WebGLContextGroup> create();
 
     void addContext(WebGLRenderingContextBase*);
     void removeContext(WebGLRenderingContextBase*);
@@ -58,6 +59,9 @@ public:
 
     void loseContextGroup(WebGLRenderingContextBase::LostContextMode);
 
+    void trace(Visitor*);
+    void clearWeakMembers(Visitor*);
+
   private:
     friend class WebGLObject;
 
@@ -65,8 +69,17 @@ public:
 
     void detachAndRemoveAllObjects();
 
-    HashSet<WebGLRenderingContextBase*> m_contexts;
-    HashSet<WebGLSharedObject*> m_groupObjects;
+    WillBeHeapHashSet<RawPtrWillBeWeakMember<WebGLRenderingContextBase> > m_contexts;

[sof, 2014/07/01 13:54:11]

Refer to the rendering contexts weakly, so as to not keep them alive when/if the
context group is the only reference.

The weak collecion serves another purpose also: being able to catch when all the
rendering contexts are about to disappear. At that point we have to evict all
the group objects, which we also keep references to weakly. See the declaration
below and clearWeakMembers() method for how that is currently handled.

+    WillBeHeapHashSet<RawPtrWillBeWeakMember<WebGLSharedObject> > m_groupObjects;
+
+#if ENABLE(OILPAN)
+    // Oilpan: Weak context references are kept, so in order to handle
+    // the case where all contexts fall away and the group objects
+    // will have to be flushed, we save away a 3D context object during
+    // tracing. It will be used during the weak callback only and cleared
+    // then.
+    blink::WebGraphicsContext3D* m_savedContext;
+#endif
 };
 
 } // namespace WebCore