Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/html/canvas/WebGLRenderingContextBase.h

 /*
  * Copyright (C) 2009 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 78 matching lines @@
 class WebGLShader;
 class WebGLShaderPrecisionFormat;
 class WebGLSharedObject;
 class WebGLTexture;
 class WebGLUniformLocation;
 class WebGLVertexArrayObjectOES;
 
 class WebGLRenderingContextLostCallback;
 class WebGLRenderingContextErrorMessageCallback;
 
-class WebGLRenderingContextBase: public CanvasRenderingContext, public ActiveDOMObject, private Page::MultisamplingChangedObserver {
+class WebGLRenderingContextBase: public CanvasRenderingContext, public ActiveDOMObject, public Page::MultisamplingChangedObserver {
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(WebGLRenderingContextBase);
 public:
     virtual ~WebGLRenderingContextBase();
 
     virtual bool is3d() const OVERRIDE { return true; }
     virtual bool isAccelerated() const OVERRIDE { return true; }
     virtual unsigned version() const = 0;
     virtual String contextName() const = 0;
     virtual void registerContextExtensions() = 0;
 
     static unsigned getWebGLVersion(const CanvasRenderingContext*);
@@ skipping 806 matching lines @@
     // If the vector is empty, return the maximum allowed active context number.
     static size_t oldestContextIndex();
     static IntSize oldestContextSize();
 };
 
 DEFINE_TYPE_CASTS(WebGLRenderingContextBase, CanvasRenderingContext, context, context->is3d(), context.is3d());
 
 } // namespace WebCore
 
 #endif // WebGLRenderingContextBase_h