Implement OffscreenCanvas.getContext('webgl')

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef OffscreenCanvas_h
 #define OffscreenCanvas_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "platform/geometry/IntSize.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class CanvasContextCreationAttributes;
 class ImageBitmap;
+class OffscreenCanvasRenderingContext2DOrWebGLRenderingContextOrWebGL2RenderingContext;
+typedef OffscreenCanvasRenderingContext2DOrWebGLRenderingContextOrWebGL2RenderingContext OffscreenRenderingContext;
 
 class CORE_EXPORT OffscreenCanvas final : public GarbageCollectedFinalized<OffscreenCanvas>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static OffscreenCanvas* create(unsigned width, unsigned height);
     ~OffscreenCanvas();
 
     // IDL attributes
     unsigned width() const { return m_size.width(); }
     unsigned height() const { return m_size.height(); }
@@ skipping 20 matching lines @@
     static CanvasRenderingContextFactory* getRenderingContextFactory(int);
 
     Member<CanvasRenderingContext> m_context;
     WeakMember<HTMLCanvasElement> m_canvas;
     IntSize m_size;
 };
 
 } // namespace blink
 
 #endif // OffscreenCanvas_h