Implement a Hit Test Cache.

Source/core/layout/LayoutInline.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 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 159 matching lines @@
 
     virtual InlineFlowBox* createInlineFlowBox(); // Subclassed by SVG and Ruby
 
     virtual void dirtyLinesFromChangedChild(LayoutObject* child) override final { m_lineBoxes.dirtyLinesFromChangedChild(this, child); }
 
     virtual LayoutUnit lineHeight(bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override final;
     virtual int baselinePosition(FontBaseline, bool firstLine, LineDirectionMode, LinePositionMode = PositionOnContainingLine) const override final;
 
     virtual void childBecameNonInline(LayoutObject* child) override final;
 
-    virtual void updateHitTestResult(HitTestResult&, const LayoutPoint&) override final;
+    virtual void updateHitTestResult(HitTestResult&, const LayoutPoint&, const LayoutRect&) override final;
 
     virtual void imageChanged(WrappedImagePtr, const IntRect* = 0) override final;
 
     virtual void addAnnotatedRegions(Vector<AnnotatedRegionValue>&) override final;
 
     virtual void updateFromStyle() override final;
 
     LayoutInline* clone() const;
 
     LayoutBoxModelObject* continuationBefore(LayoutObject* beforeChild);
 
     LayoutObjectChildList m_children;
     LineBoxList m_lineBoxes; // All of the line boxes created for this inline flow.  For example, <i>Hello<br>world.</i> will have two <i> line boxes.
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutInline, isLayoutInline());
 
 } // namespace blink
 
 #endif // LayoutInline_h