RenderTextHarfBuzz: Implement font fallback for Win and Linux

ui/gfx/font_fallback_win.h

 // Copyright (c) 2012 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_FONT_FALLBACK_WIN_H_
 #define UI_GFX_FONT_FALLBACK_WIN_H_
 
 #include <string>
 #include <vector>
 
 #include "ui/gfx/font.h"
+#include "ui/gfx/font_fallback.h"
 
 namespace gfx {
 
 // Internals of font_fallback_win.cc exposed for testing.
 namespace internal {
 
 // Parses comma separated SystemLink |entry|, per the format described here:
 // http://msdn.microsoft.com/en-us/goglobal/bb688134.aspx
 //
 // Sets |filename| and |font_name| respectively. If a field is not present
 // or could not be parsed, the corresponding parameter will be cleared.
 void GFX_EXPORT ParseFontLinkEntry(const std::string& entry,
                                   std::string* filename,
                                   std::string* font_name);
 
 // Parses a font |family| in the format "FamilyFoo & FamilyBar (TrueType)".
 // Splits by '&' and strips off the trailing parenthesized expression.
 void GFX_EXPORT ParseFontFamilyString(const std::string& family,
                                      std::vector<std::string>* font_names);
 
-}  // namespace internal
-
 // Iterator over linked fallback fonts for a given font. The linked font chain
 // comes from the Windows registry, but gets cached between uses.
 class GFX_EXPORT LinkedFontsIterator {
  public:
   // Instantiates the iterator over the linked font chain for |font|. The first
   // item will be |font| itself.
   explicit LinkedFontsIterator(Font font);
   virtual ~LinkedFontsIterator();
 
   // Sets the font that would be returned by the next call to |NextFont()|,
@@ skipping 26 matching lines @@
 
   // List of linked fonts; weak pointer.
   const std::vector<Font>* linked_fonts_;
 
   // Index of the current entry in the |linked_fonts_| list.
   size_t linked_font_index_;
 
   DISALLOW_COPY_AND_ASSIGN(LinkedFontsIterator);
 };
 
+}  // namespace internal
+
+// Finds a fallback font to render the specified |text| with respect to an
+// initial |font|. Returns the resulting font via out param |result|. Returns
+// |true| if a fallback font was found.
+bool GetUniscribeFallbackFont(const Font& font,
+                              const wchar_t* text,
+                              int text_length,
+                              Font* result);
+
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_FALLBACK_WIN_H_