Implement a Hit Test Cache.

Source/core/layout/LayoutTextFragment.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 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 60 matching lines @@
     FirstLetterPseudoElement* firstLetterPseudoElement() const { return m_firstLetterPseudoElement; }
 
     void setIsRemainingTextLayoutObject(bool isRemainingText) { m_isRemainingTextLayoutObject = isRemainingText; }
     bool isRemainingTextLayoutObject() const { return m_isRemainingTextLayoutObject; }
 
 private:
     LayoutBlock* blockForAccompanyingFirstLetter() const;
     virtual UChar previousCharacter() const override;
 
     Text* associatedTextNode() const;
-    void updateHitTestResult(HitTestResult&, const LayoutPoint&) override;
+    void updateHitTestResult(HitTestResult&, const LayoutPoint&, const LayoutRect&) override;
 
     unsigned m_start;
     unsigned m_end;
     bool m_isRemainingTextLayoutObject;
     RefPtr<StringImpl> m_contentString;
     // Reference back to FirstLetterPseudoElement; cleared by FirstLetterPseudoElement::detach() if
     // it goes away first.
     FirstLetterPseudoElement* m_firstLetterPseudoElement;
 };
 
 DEFINE_TYPE_CASTS(LayoutTextFragment, LayoutObject, object, toLayoutText(object)->isTextFragment(), toLayoutText(object).isTextFragment());
 
 } // namespace blink
 
 #endif // LayoutTextFragment_h