RenderTextHarfBuzz: Implement font fallback for Win and Linux

ui/gfx/font_fallback_win.cc

 // 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.
 
 #include "ui/gfx/font_fallback_win.h"
 
 #include <map>
 
 #include "base/memory/singleton.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/registry.h"
 #include "ui/gfx/font.h"
+#include "ui/gfx/font_fallback.h"
 
 namespace gfx {
 
 namespace {
 
 // Queries the registry to get a mapping from font filenames to font names.
 void QueryFontsFromRegistry(std::map<std::string, std::string>* map) {
   const wchar_t* kFonts =
       L"Software\\Microsoft\\Windows NT\\CurrentVersion\\Fonts";
 
@@ skipping 154 matching lines @@
   if (!font_names->empty()) {
     const size_t index = font_names->back().find('(');
     if (index != std::string::npos) {
       font_names->back().resize(index);
       base::TrimWhitespace(font_names->back(), base::TRIM_TRAILING,
                            &font_names->back());
     }
   }
 }
 
-}  // namespace internal
-
 LinkedFontsIterator::LinkedFontsIterator(Font font)
     : original_font_(font),
       next_font_set_(false),
       linked_fonts_(NULL),
       linked_font_index_(0) {
   SetNextFont(original_font_);
 }
 
 LinkedFontsIterator::~LinkedFontsIterator() {
 }
@@ skipping 35 matching lines @@
   //
   // Note: One possibility would be to always merge both lists of fonts,
   //       but it is not clear whether there are any real world scenarios
   //       where this would actually help.
   if (fonts->empty())
     fonts = font_link->GetLinkedFonts(current_font_);
 
   return fonts;
 }
 
+}  // namespace internal
+
+std::vector<std::string> GetFallbackFontFamilies(std::string font_family) {
+  internal::LinkedFontsIterator linked_fonts(Font(font_family, 10));
+  std::vector<std::string> fallback_fonts;
+  Font current;
+  while (linked_fonts.NextFont(&current))
+    fallback_fonts.push_back(current.GetFontName());
+  return fallback_fonts;
+}
+
 }  // namespace gfx