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

Source/core/html/canvas/WebGLSharedObject.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 22 matching lines @@
 namespace WebCore {
 
 WebGLSharedObject::WebGLSharedObject(WebGLRenderingContextBase* context)
     : WebGLObject(context),
       m_contextGroup(context->contextGroup())
 {
 }
 
 WebGLSharedObject::~WebGLSharedObject()
 {
+#if !ENABLE(OILPAN)

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

If this object dies at the same time as its context group object (and,
transitively, all the rendering contexts that refer to it), then we do not
delete its underlying resource. The assumption is that the rendering context
will tear down all when finalized & it invoking destroyContext().

In all other cases, we assume that the disappearance of the rendering context
will detach the shared objects (via the context group object.)

     if (m_contextGroup)
         m_contextGroup->removeObject(this);
+#endif
 }
 
 void WebGLSharedObject::detachContextGroup()
 {
     detach();
     if (m_contextGroup) {
         deleteObject(0);
         m_contextGroup->removeObject(this);
-        m_contextGroup = 0;
+        m_contextGroup = nullptr;
     }
 }
 
 blink::WebGraphicsContext3D* WebGLSharedObject::getAWebGraphicsContext3D() const
 {
     return m_contextGroup ? m_contextGroup->getAWebGraphicsContext3D() : 0;
 }
 
+void WebGLSharedObject::trace(Visitor* visitor)
+{
+    visitor->trace(m_contextGroup);
+    WebGLObject::trace(visitor);
 }
+
+}