RenderTextHarfBuzz: Implement font fallback for Win and Linux

ui/gfx/render_text_win.cc

Index: ui/gfx/render_text_win.cc
diff --git a/ui/gfx/render_text_win.cc b/ui/gfx/render_text_win.cc
index f79577fde0aa9314cd61ddd7b5f209ee71ae1ae4..122d7c15a5096f1c0f8ffd7df0544578e6572dcc 100644
--- a/ui/gfx/render_text_win.cc
+++ b/ui/gfx/render_text_win.cc
@@ -15,7 +15,7 @@
 #include "base/win/windows_version.h"
 #include "third_party/icu/source/common/unicode/uchar.h"
 #include "ui/gfx/canvas.h"
-#include "ui/gfx/font_fallback_win.h"
+#include "ui/gfx/font_fallback.h"
 #include "ui/gfx/font_smoothing_win.h"
 #include "ui/gfx/platform_font_win.h"
 #include "ui/gfx/utf16_indexing.h"
@@ -1060,7 +1060,8 @@ void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
   const size_t run_length = run->range.length();
   const wchar_t* run_text = &(GetLayoutText()[run->range.start()]);
   Font original_font = run->font;
-  LinkedFontsIterator fonts(original_font);
+  std::vector<std::string> fallback_fonts =
+      GetFallbackFontFamilies(original_font.GetFontName());
   bool tried_cached_font = false;
   bool tried_fallback = false;
   // Keep track of the font that is able to display the greatest number of
@@ -1068,11 +1069,14 @@ void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
   // in the case where no font is able to display the entire run.
   int best_partial_font_missing_char_count = INT_MAX;
   Font best_partial_font = original_font;
-  Font current_font;
 
   run->logical_clusters.reset(new WORD[run_length]);
-  while (fonts.NextFont(&current_font)) {
-    HRESULT hr = ShapeTextRunWithFont(run, current_font);
+  Font current_font;
+  bool next_font_set = false;
+  for (size_t i = 0; i < fallback_fonts.size();) {
+    HRESULT hr = ShapeTextRunWithFont(run, next_font_set ?
+        current_font : Font(fallback_fonts[i++], original_font.GetFontSize()));
+    next_font_set = false;
 
     bool glyphs_missing = false;
     if (hr == USP_E_SCRIPT_NOT_IN_FONT) {
@@ -1106,7 +1110,8 @@ void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
       std::map<std::string, Font>::const_iterator it =
           successful_substitute_fonts_.find(original_font.GetFontName());
       if (it != successful_substitute_fonts_.end()) {
-        fonts.SetNextFont(it->second);
+        current_font = it->second;
+        next_font_set = true;
         continue;
       }
     }
@@ -1120,7 +1125,8 @@ void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
       Font fallback_font;
       if (ChooseFallbackFont(cached_hdc_, run->font, run_text, run_length,
                              &fallback_font)) {
-        fonts.SetNextFont(fallback_font);
+        current_font = fallback_font;
+        next_font_set = true;
         continue;
       }
     }