Make OffscreenCanvasRenderingContext2D renderable on a worker

third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasRenderingContext.h

 // Copyright 2016 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 OffscreenCanvasRenderingContext_h
 #define OffscreenCanvasRenderingContext_h
 
 #include "modules/ModulesExport.h"
 #include "modules/offscreencanvas/OffscreenCanvas.h"
 
 namespace blink {
 
+class ImageBitmap;
+
 class MODULES_EXPORT OffscreenCanvasRenderingContext : public GarbageCollectedFinalized<OffscreenCanvasRenderingContext>, public ScriptWrappable {
     WTF_MAKE_NONCOPYABLE(OffscreenCanvasRenderingContext);
 public:
     virtual ~OffscreenCanvasRenderingContext() { }
     enum ContextType {
         Context2d = 0,
         ContextWebgl = 1,
         ContextWebgl2 = 2,
         ContextTypeCount
     };
     static ContextType contextTypeFromId(const String& id);
 
     OffscreenCanvas* offscreenCanvas() const { return m_offscreenCanvas; }
     virtual ContextType contextType() const = 0;
+    virtual PassRefPtrWillBeRawPtr<ImageBitmap> transferToImageBitmap(ExceptionState&) = 0;
 
     virtual bool is2d() const { return false; }
 
 protected:
     OffscreenCanvasRenderingContext(OffscreenCanvas*);
     DECLARE_VIRTUAL_TRACE();
 
 private:
     Member<OffscreenCanvas> m_offscreenCanvas;
 };
 
 } // namespace blink
 
 #endif // OffscreenCanvasRenderingContext_h