RenderTextHarfBuzz: Try fallback fonts of the Uniscribe font while shaping

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 f68224bd101c46aeb4077c9c398b3ced5d3bcf30..0ca29577399f118ebdb4f0109b480a844d49bf6f 100644
--- a/ui/gfx/render_text_win.cc
+++ b/ui/gfx/render_text_win.cc
@@ -1033,8 +1033,10 @@ void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
   // Try finding a fallback font using a meta file.
   // TODO(msw|asvitkine): Support RenderText's font_list()?
   Font uniscribe_font;
+  bool got_uniscribe_font = false;
   if (GetUniscribeFallbackFont(original_font, run_text, run_length,
                                &uniscribe_font)) {
+    got_uniscribe_font = true;
     current_font = uniscribe_font;
     missing_count = CountCharsWithMissingGlyphs(run,
         ShapeTextRunWithFont(run, current_font));
@@ -1066,18 +1068,21 @@ void RenderTextWin::LayoutTextRun(internal::TextRun* run) {
   }
 
   // Try fonts in the fallback list of the Uniscribe font.
-  fonts = GetFallbackFontFamilies(uniscribe_font.GetFontName());
-  for (size_t i = 1; i < fonts.size(); ++i) {
-    current_font = Font(fonts[i], original_font.GetFontSize());
-    missing_count = CountCharsWithMissingGlyphs(run,
-      ShapeTextRunWithFont(run, current_font));
-    if (missing_count == 0) {
-      successful_substitute_fonts_[original_font.GetFontName()] = current_font;
-      return;
-    }
-    if (missing_count < best_partial_font_missing_char_count) {
-      best_partial_font_missing_char_count = missing_count;
-      best_partial_font = current_font;
+  if (got_uniscribe_font) {
+    fonts = GetFallbackFontFamilies(uniscribe_font.GetFontName());
+    for (size_t i = 1; i < fonts.size(); ++i) {
+      current_font = Font(fonts[i], original_font.GetFontSize());
+      missing_count = CountCharsWithMissingGlyphs(run,
+          ShapeTextRunWithFont(run, current_font));
+      if (missing_count == 0) {
+        successful_substitute_fonts_[original_font.GetFontName()] =
+            current_font;
+        return;
+      }
+      if (missing_count < best_partial_font_missing_char_count) {
+        best_partial_font_missing_char_count = missing_count;
+        best_partial_font = current_font;
+      }
     }
   }