Implement OffscreenCanvas.getContext('webgl')

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 24 matching lines @@
 class SkCanvas;
 
 namespace blink { class WebLayer; }
 
 namespace blink {
 
 class CanvasImageSource;
 class HTMLCanvasElement;
 class ImageData;
 
-class CORE_EXPORT CanvasRenderingContext : public GarbageCollectedFinalized<CanvasRenderingContext>, public ScriptWrappable {
+class CORE_EXPORT CanvasRenderingContext : public GarbageCollectedFinalized<CanvasRenderingContext> {
     WTF_MAKE_NONCOPYABLE(CanvasRenderingContext);
 public:
     virtual ~CanvasRenderingContext() { }
 
     // A Canvas can either be "2D" or "webgl" but never both. If you request a 2D canvas and the existing
     // context is already 2D, just return that. If the existing context is WebGL, then destroy it
     // before creating a new 2D context. Vice versa when requesting a WebGL canvas. Requesting a
     // context with any other type string will destroy any existing context.
     enum ContextType {
         // Do not change assigned numbers of existing items: add new features to the end of the list.
@@ skipping 70 matching lines @@
 
 private:
     Member<HTMLCanvasElement> m_canvas;
     HashSet<String> m_cleanURLs;
     HashSet<String> m_dirtyURLs;
 };
 
 } // namespace blink
 
 #endif