Change Font::offsetForPositionForComplexText to use CachingWordShapeIterator

Source/platform/fonts/shaping/HarfBuzzShaper.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 44 matching lines @@
 public:
     static PassRefPtr<ShapeResult> create(const Font* font,
         unsigned numCharacters, TextDirection direction)
     {
         return adoptRef(new ShapeResult(font, numCharacters, direction));
     }
     ~ShapeResult();
 
     float width() { return m_width; }
     FloatRect bounds() { return m_glyphBoundingBox; }
-    int offsetForPosition(float targetX);
     unsigned numCharacters() const { return m_numCharacters; }
     void fallbackFonts(HashSet<const SimpleFontData*>*) const;
 
+    static int offsetForPosition(Vector<RefPtr<ShapeResult>>&,
+        const TextRun&, float targetX);
     static float fillGlyphBuffer(Vector<RefPtr<ShapeResult>>&,
         GlyphBuffer*, const TextRun&, unsigned from, unsigned to);
     static float fillGlyphBufferForTextEmphasis(Vector<RefPtr<ShapeResult>>&,
         GlyphBuffer*, const TextRun&, const GlyphData* emphasisData,
         unsigned from, unsigned to);
     static FloatRect selectionRect(Vector<RefPtr<ShapeResult>>&,
         TextDirection, float totalWidth, const FloatPoint&, int height,
         unsigned from, unsigned to);
 
     unsigned numberOfRunsForTesting() const;
     bool runInfoForTesting(unsigned runIndex, unsigned& startIndex,
         unsigned& numGlyphs, hb_script_t&);
     uint16_t glyphForTesting(unsigned runIndex, size_t glyphIndex);
     float advanceForTesting(unsigned runIndex, size_t glyphIndex);
 
 private:
     struct RunInfo;
 
     ShapeResult(const Font*, unsigned numCharacters, TextDirection);
 
+    int offsetForPosition(float targetX);
     template<TextDirection>
     float fillGlyphBufferForRun(GlyphBuffer*, const RunInfo*,
         float initialAdvance, unsigned from, unsigned to, unsigned runOffset);
 
     float fillGlyphBufferForTextEmphasisRun(GlyphBuffer*, const RunInfo*,
         const TextRun&, const GlyphData*, float initialAdvance,
         unsigned from, unsigned to, unsigned runOffset);
 
     float m_width;
     FloatRect m_glyphBoundingBox;
@@ skipping 44 matching lines @@
     float m_letterSpacing; // Pixels to be added after each glyph.
     unsigned m_expansionOpportunityCount;
 
     Vector<hb_feature_t, 4> m_features;
     Vector<HarfBuzzRun, 16> m_harfBuzzRuns;
 };
 
 } // namespace blink
 
 #endif // HarfBuzzShaper_h