Implement a Hit Test Cache.

Source/platform/geometry/LayoutRect.cpp

 /*
  * Copyright (c) 2012, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 144 matching lines @@
     return IntRect(location, maxPoint - location);
 }
 
 LayoutRect enclosingLayoutRect(const FloatRect& rect)
 {
     LayoutPoint location = flooredLayoutPoint(rect.minXMinYCorner());
     LayoutPoint maxPoint = ceiledLayoutPoint(rect.maxXMaxYCorner());
     return LayoutRect(location, maxPoint - location);
 }
 
+LayoutRect boundingRect(const LayoutPoint& point)
+{
+    return LayoutRect(point, LayoutSize(LayoutUnit::epsilonUnit(), LayoutUnit::epsilonUnit()));
+}
+
 } // namespace blink