Implement a Hit Test Cache.

Source/core/layout/LayoutTextFragment.cpp

 /*
  * (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 137 matching lines @@
     if (node->isFirstLetterPseudoElement()) {
         FirstLetterPseudoElement* pseudo = toFirstLetterPseudoElement(node);
         LayoutObject* nextLayoutObject = FirstLetterPseudoElement::firstLetterTextLayoutObject(*pseudo);
         if (!nextLayoutObject)
             return nullptr;
         node = nextLayoutObject->node();
     }
     return (node && node->isTextNode()) ? toText(node) : nullptr;
 }
 
-void LayoutTextFragment::updateHitTestResult(HitTestResult& result, const LayoutPoint& point)
+void LayoutTextFragment::updateHitTestResult(HitTestResult& result, const LayoutPoint& point, const LayoutRect& rect)
 {
     if (result.innerNode())
         return;
 
-    LayoutObject::updateHitTestResult(result, point);
+    LayoutObject::updateHitTestResult(result, point, rect);
 
     // If we aren't part of a first-letter element, or if we
     // are part of first-letter but we're the remaining text then return.
     if (m_isRemainingTextLayoutObject || !firstLetterPseudoElement())
         return;
     result.setInnerNode(firstLetterPseudoElement());
 }
 
 } // namespace blink