Use a union typdef for the return type of canvas.getContext

third_party/WebKit/Source/core/html/canvas/CanvasRenderingContext.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 59 matching lines @@
     void deref() { m_canvas->deref(); }
 #endif
 
     HTMLCanvasElement* canvas() const { return m_canvas; }
 
     virtual ContextType getContextType() const = 0;
     virtual bool isAccelerated() const { return false; }
     virtual bool hasAlpha() const { return true; }
     virtual void setIsHidden(bool) = 0;
     virtual bool isContextLost() const { return true; }
+    virtual void setCanvasGetContextResult(RenderingContext&) = 0;
 
     // Return true if the content is updated.
     virtual bool paintRenderingResultsToCanvas(SourceDrawingBuffer) { return false; }
 
     virtual WebLayer* platformLayer() const { return nullptr; }
 
     enum LostContextMode {
         NotLostContext,
 
         // Lost context occurred at the graphics system level.
@@ skipping 39 matching lines @@
 
 private:
     RawPtrWillBeMember<HTMLCanvasElement> m_canvas;
     HashSet<String> m_cleanURLs;
     HashSet<String> m_dirtyURLs;
 };
 
 } // namespace blink
 
 #endif