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

Source/core/html/canvas/WebGLSharedObject.h

 /*
  * 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 36 matching lines @@
     virtual bool isShader() const { return false; }
     virtual bool isTexture() const { return false; }
 
     virtual bool validate(const WebGLContextGroup* contextGroup, const WebGLRenderingContextBase*) const OVERRIDE FINAL
     {
         return contextGroup == m_contextGroup;
     }
 
     void detachContextGroup();
 
+    virtual void trace(Visitor*) OVERRIDE;
+
 protected:
     WebGLSharedObject(WebGLRenderingContextBase*);
 
     virtual bool hasGroupOrContext() const OVERRIDE FINAL
     {
         return m_contextGroup;
     }
 
     virtual blink::WebGraphicsContext3D* getAWebGraphicsContext3D() const OVERRIDE FINAL;
 
 private:
-    WebGLContextGroup* m_contextGroup;
+    RawPtrWillBeMember<WebGLContextGroup> m_contextGroup;
 };
 
 } // namespace WebCore
 
 #endif // WebGLSharedObject_h