Implement basic parts of hit regions on canvas2d.

Source/platform/graphics/Path.h

 /*
  * Copyright (C) 2003, 2006, 2009 Apple Inc. All rights reserved.
  *               2006 Rob Buis <buis@kde.org>
  * Copyright (C) 2007-2008 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
@@ skipping 125 matching lines @@
     void translate(const FloatSize&);
 
     const SkPath& skPath() const { return m_path; }
 
     void apply(void* info, PathApplierFunction) const;
     void transform(const AffineTransform&);
 
     void addPathForRoundedRect(const FloatRect&, const FloatSize& topLeftRadius, const FloatSize& topRightRadius, const FloatSize& bottomLeftRadius, const FloatSize& bottomRightRadius);
     void addBeziersForRoundedRect(const FloatRect&, const FloatSize& topLeftRadius, const FloatSize& topRightRadius, const FloatSize& bottomLeftRadius, const FloatSize& bottomRightRadius);
 
+    bool subtractPath(const Path&);
+
     // Updates the path to the union (inclusive-or) of itself with the given argument.
     bool unionPath(const Path& other);
 
 private:
     void addEllipse(const FloatPoint&, float radiusX, float radiusY, float startAngle, float endAngle, bool anticlockwise);
 
     SkPath m_path;
 };
 
 #if !ASSERT_DISABLED
 PLATFORM_EXPORT bool ellipseIsRenderable(float startAngle, float endAngle);
 #endif
 
 }
 
 #endif