This CL implements the first draft of Canvas 2D Context Attributes, aka getContext('2d', { alpha: f…

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 36 matching lines @@
 public:
     virtual ~CanvasRenderingContext() { }
 
     void ref() { m_canvas->ref(); }
     void deref() { m_canvas->deref(); }
     HTMLCanvasElement* canvas() const { return m_canvas; }
 
     virtual bool is2d() const { return false; }
     virtual bool is3d() const { return false; }
     virtual bool isAccelerated() const { return false; }
+    virtual bool hasAlpha() const { return true; }
 
     virtual void paintRenderingResultsToCanvas() {}
 
     virtual PlatformLayer* platformLayer() const { return 0; }
 
 protected:
     CanvasRenderingContext(HTMLCanvasElement*);
     bool wouldTaintOrigin(const CanvasPattern*);
     bool wouldTaintOrigin(const HTMLCanvasElement*);
     bool wouldTaintOrigin(const HTMLImageElement*);
     bool wouldTaintOrigin(const HTMLVideoElement*);
     bool wouldTaintOrigin(const KURL&);
 
     template<class T> void checkOrigin(const T* arg)
     {
         if (wouldTaintOrigin(arg))
             canvas()->setOriginTainted();
     }
     void checkOrigin(const KURL&);
 
 private:
     HTMLCanvasElement* m_canvas;
     HashSet<String> m_cleanURLs;
 };
 
 } // namespace WebCore
 
 #endif