Implement a Hit Test Cache.

Source/core/layout/LayoutBlock.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 268 matching lines @@
     virtual void adjustInlineDirectionLineBounds(unsigned /* expansionOpportunityCount */, float& /* logicalLeft */, float& /* logicalWidth */) const { }
 
     virtual void computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const override;
     virtual void computePreferredLogicalWidths() override;
     void adjustIntrinsicLogicalWidthsForColumns(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const;
 
     virtual int firstLineBoxBaseline() const override;
     virtual int inlineBlockBaseline(LineDirectionMode) const override;
     int lastLineBoxBaseline(LineDirectionMode) const;
 
-    virtual void updateHitTestResult(HitTestResult&, const LayoutPoint&) override;
+    virtual void updateHitTestResult(HitTestResult&, const LayoutPoint&, const LayoutRect&) override;
 
     // Delay update scrollbar until finishDelayUpdateScrollInfo() will be
     // called. This function is used when a flexbox is laying out its
     // descendant. If multiple calls are made to startDelayUpdateScrollInfo(),
     // finishDelayUpdateScrollInfo() will do nothing until finishDelayUpdateScrollInfo()
     // is called the same number of times.
     static void startDelayUpdateScrollInfo();
     static void finishDelayUpdateScrollInfo();
 
     void updateScrollInfoAfterLayout();
@@ skipping 175 matching lines @@
     // FIXME: This is temporary as we move code that accesses block flow
     // member variables out of LayoutBlock and into LayoutBlockFlow.
     friend class LayoutBlockFlow;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlock, isLayoutBlock());
 
 } // namespace blink
 
 #endif // LayoutBlock_h