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 32 matching lines @@
     if (m_contextGroup)
         m_contextGroup->removeObject(this);
 }
 
 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;
 }
 
 }