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

Source/core/html/canvas/Canvas2DContextAttributes.h

 /*
  * Copyright (c) 2013, Google 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:
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following disclaimer
@@ skipping 25 matching lines @@
 enum Canvas2DContextStorage {
     PersistentStorage,
     DiscardableStorage
 };
 
 class Canvas2DContextAttributes : public CanvasContextAttributes, public ScriptWrappable {
 public:
     virtual ~Canvas2DContextAttributes();
 
     // Create a new attributes object
-    static PassRefPtr<Canvas2DContextAttributes> create();
+    static PassRefPtrWillBeRawPtr<Canvas2DContextAttributes> create();
 
     // Whether or not the drawing buffer has an alpha channel; default=true
     bool alpha() const;
     void setAlpha(bool);
 
     String storage() const;
     void setStorage(const String&);
     Canvas2DContextStorage parsedStorage() const;
 
 protected:
     Canvas2DContextAttributes();
 
     bool m_alpha;
     Canvas2DContextStorage m_storage;
 };
 
 } // namespace WebCore
 
 #endif // Canvas2DContextAttributes_h