RenderTextHarfBuzz: Implement font fallback for Win and Linux

ui/gfx/render_text_harfbuzz.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_RENDER_TEXT_HARFBUZZ_H_
 #define UI_GFX_RENDER_TEXT_HARFBUZZ_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/scoped_vector.h"
 #include "third_party/harfbuzz-ng/src/hb.h"
@@ skipping 11 matching lines @@
 
   // Returns the index of the first glyph that corresponds to the character at
   // |pos|.
   size_t CharToGlyph(size_t pos) const;
 
   // Returns the corresponding glyph range of the given character range.
   // |range| is in text-space (0 corresponds to |GetLayoutText()[0]|). Returned
   // value is in run-space (0 corresponds to the first glyph in the run).
   Range CharRangeToGlyphRange(const Range& range) const;
 
-  // Returns whether the given shaped run contains any missing glyphs.
-  bool HasMissingGlyphs() const;
+  // Returns the number of missing glyphs in the shaped text run.
+  size_t CountMissingGlyphs() const;
 
   // Returns the X coordinate of the leading or |trailing| edge of the glyph
   // starting at |text_index|, relative to the left of the text (not the view).
   int GetGlyphXBoundary(size_t text_index, bool trailing) const;
 
   int width;
   int preceding_run_widths;
   Range range;
   bool is_rtl;
   UBiDiLevel level;
@@ skipping 61 matching lines @@
   SelectionModel FirstSelectionModelInsideRun(
       const internal::TextRunHarfBuzz* run);
   SelectionModel LastSelectionModelInsideRun(
       const internal::TextRunHarfBuzz* run);
 
   // Break the text into logical runs and populate the visual <-> logical maps.
   void ItemizeText();
 
   // Shape the glyphs needed for the text |run|.
   void ShapeRun(internal::TextRunHarfBuzz* run);
+  void ShapeRunWithFont(internal::TextRunHarfBuzz* run,
+                        const std::string& font);
 
   // Text runs in logical order.
   ScopedVector<internal::TextRunHarfBuzz> runs_;
 
   // Maps visual run indices to logical run indices and vice versa.
   std::vector<int32_t> visual_to_logical_;
   std::vector<int32_t> logical_to_visual_;
 
   bool needs_layout_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderTextHarfBuzz);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_HARFBUZZ_H_