Change Font::offsetForPositionForComplexText to use CachingWordShapeIterator

Source/platform/fonts/Font.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (c) 2007, 2008, 2010 Google 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
@@ skipping 686 matching lines @@
 {
     CachingWordShaper& shaper = m_fontFallbackList->cachingWordShaper();
     float width = shaper.width(this, run, fallbackFonts, glyphBounds);
     return width;
 }
 
 // Return the code point index for the given |x| offset into the text run.
 int Font::offsetForPositionForComplexText(const TextRun& run, float xFloat,
     bool includePartialGlyphs) const
 {
-    HarfBuzzShaper shaper(this, run);
-    RefPtr<ShapeResult> shapeResult = shaper.shapeResult();
-    if (!shapeResult)
-        return 0;
-    return shapeResult->offsetForPosition(xFloat);
+    CachingWordShaper& shaper = m_fontFallbackList->cachingWordShaper();
+    return shaper.offsetForPosition(this, run, xFloat);
 }
 
 // Return the rectangle for selecting the given range of code-points in the TextRun.
 FloatRect Font::selectionRectForComplexText(const TextRun& run,
     const FloatPoint& point, int height, int from, int to) const
 {
     CachingWordShaper& shaper = m_fontFallbackList->cachingWordShaper();
     return shaper.selectionRect(this, run, point, height, from, to);
 }
 
@@ skipping 109 matching lines @@
 {
     return m_fontFallbackList && m_fontFallbackList->loadingCustomFonts();
 }
 
 bool Font::isFallbackValid() const
 {
     return !m_fontFallbackList || m_fontFallbackList->isValid();
 }
 
 } // namespace blink