Canvas2d: Implement rerouting event by hit region's control.

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

 /*
  * Copyright (C) 2004, 2006, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 164 matching lines @@
     void createImageBufferUsingSurfaceForTesting(PassOwnPtr<ImageBufferSurface>);
 
     static void registerRenderingContextFactory(PassOwnPtr<CanvasRenderingContextFactory>);
     void updateExternallyAllocatedMemory() const;
 
     void styleDidChange(const ComputedStyle* oldStyle, const ComputedStyle& newStyle);
 
     void notifyListenersCanvasChanged();
 
     bool isSupportedInteractiveCanvasFallback(const Element&);
+    std::pair<Element*, String> getControlAndIdIfHitRegionExists(const LayoutPoint&);
 
 protected:
     void didMoveToNewDocument(Document& oldDocument) override;
 
 private:
     explicit HTMLCanvasElement(Document&);
 
     using ContextFactoryVector = Vector<OwnPtr<CanvasRenderingContextFactory>>;
     static ContextFactoryVector& renderingContextFactories();
     static CanvasRenderingContextFactory* getRenderingContextFactory(int);
@@ skipping 35 matching lines @@
     mutable bool m_didFailToCreateImageBuffer;
     bool m_imageBufferIsClear;
     OwnPtr<ImageBuffer> m_imageBuffer;
 
     mutable RefPtr<Image> m_copiedImage; // FIXME: This is temporary for platforms that have to copy the image buffer to render (and for CSSCanvasValue).
 };
 
 } // namespace blink
 
 #endif // HTMLCanvasElement_h