[Oilpan] Migrate classes under module/webgl onto oilpan heap

Source/modules/webgl/WebGLContextObject.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 39 matching lines @@
     detach();
     if (m_context) {
         deleteObject(m_context->webContext());
         m_context->removeContextObject(this);
         m_context = nullptr;
     }
 }
 
 WebGraphicsContext3D* WebGLContextObject::getAWebGraphicsContext3D() const
 {
-    return m_context ? m_context->webContext() : 0;
+    return m_context ? m_context->webContext() : nullptr;
 }
 
 DEFINE_TRACE(WebGLContextObject)
 {
     visitor->trace(m_context);
     WebGLObject::trace(visitor);
 }
 
 } // namespace blink