Implement basic parts of hit regions on canvas2d.

Source/platform/graphics/GraphicsContext.h

 /*
  * Copyright (C) 2003, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008-2009 Torch Mobile, Inc.
  * Copyright (C) 2013 Google 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.
@@ skipping 351 matching lines @@
         LeftEdge = 1 << 4
     };
     typedef unsigned Edges;
     void drawInnerShadow(const RoundedRect&, const Color& shadowColor, const IntSize shadowOffset, int shadowBlur, int shadowSpread, Edges clippedEdges = NoEdge);
 
     // This clip function is used only by <canvas> code. It allows
     // implementations to handle clipping on the canvas differently since
     // the discipline is different.
     void canvasClip(const Path&, WindRule = RULE_EVENODD);
     void clipOut(const Path&);
+    Path getCurrentClipPath();
 
     // ---------- Transformation methods -----------------
     enum IncludeDeviceScale { DefinitelyIncludeDeviceScale, PossiblyIncludeDeviceScale };
     AffineTransform getCTM(IncludeDeviceScale includeScale = PossiblyIncludeDeviceScale) const;
     void concatCTM(const AffineTransform& affine) { concat(affineTransformToSkMatrix(affine)); }
     void setCTM(const AffineTransform& affine) { setMatrix(affineTransformToSkMatrix(affine)); }
     void setMatrix(const SkMatrix&);
 
     void scale(const FloatSize&);
     void rotate(float angleInRadians);
@@ skipping 152 matching lines @@
     bool m_updatingControlTints : 1;
     bool m_accelerated : 1;
     bool m_isCertainlyOpaque : 1;
     bool m_printing : 1;
     bool m_antialiasHairlineImages : 1;
 };
 
 } // namespace WebCore
 
 #endif // GraphicsContext_h