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

third_party/WebKit/Source/modules/imagebitmap/ImageBitmapRenderingContext.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 ImageBitmapRenderingContext_h
 #define ImageBitmapRenderingContext_h
 
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/CanvasRenderingContextFactory.h"
 #include "modules/ModulesExport.h"
@@ skipping 19 matching lines @@
 
     // Script API
     void transferImageBitmap(ImageBitmap*);
 
     // CanvasRenderingContext implementation
     ContextType getContextType() const override { return CanvasRenderingContext::ContextImageBitmap; }
     bool hasAlpha() const override { return m_hasAlpha; }
     void setIsHidden(bool) override { }
     bool isContextLost() const override { return false; }
     bool paint(GraphicsContext&, const IntRect&) override;
+    void setCanvasGetContextResult(RenderingContext&) final;
 
     // TODO(junov): Implement GPU accelerated rendering using a layer bridge
     WebLayer* platformLayer() const override { return nullptr; }
     // TODO(junov): handle lost contexts when content is GPU-backed
     void loseContext(LostContextMode) override { }
 
     void stop() override;
 
     virtual ~ImageBitmapRenderingContext();
 
 private:
     ImageBitmapRenderingContext(HTMLCanvasElement*, CanvasContextCreationAttributes, Document&);
 
     bool m_hasAlpha;
     RefPtr<Image> m_image;
 };
 
 } // blink
 
 #endif