Remove duplicate fonts from the font fallback list.

ui/gfx/render_text_harfbuzz.cc

 // 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.
 
 #include "ui/gfx/render_text_harfbuzz.h"
 
 #include <limits>
 
 #include "base/i18n/bidi_line_iterator.h"
 #include "base/i18n/break_iterator.h"
@@ skipping 1284 matching lines @@
   // ensure that the fallback list covers the basic cases.
   // http://crbug.com/467459. On some Windows configurations the default font
   // could be a raster font like System, which would not give us a reasonable
   // fallback font list.
   std::vector<std::string> default_fallback_families =
       GetFallbackFontFamilies("Segoe UI");
   fallback_families.insert(fallback_families.end(),
       default_fallback_families.begin(), default_fallback_families.end());
 #endif
 
+  // Get rid of duplicate fonts in the fallback list. We use the std::unique
+  // algorithm for this. However for this function to work we need to sort
+  // the font list as the unique algorithm relies on duplicates being adjacent.
+  // TODO(ananta)
+  // Sorting the list changes the order in which fonts are evaluated. This may
+  // cause problems in the way some characters appear. It may be best to do
+  // font fallback on the same lines as blink or skia which do this based on
+  // character glyph mapping.
+  std::sort(fallback_families.begin(), fallback_families.end());
+  fallback_families.erase(std::unique(
+      fallback_families.begin(), fallback_families.end()),
+      fallback_families.end());
+
   // Try shaping with the fallback fonts.
   for (const auto& family : fallback_families) {
     if (family == primary_family)
       continue;
 #if defined(OS_WIN)
     if (family == uniscribe_family)
       continue;
 #endif
     FontRenderParamsQuery query(false);
     query.families.push_back(family);
@@ skipping 187 matching lines @@
   DCHECK(!update_layout_run_list_);
   DCHECK(!update_display_run_list_);
   return text_elided() ? display_run_list_.get() : &layout_run_list_;
 }
 
 const internal::TextRunList* RenderTextHarfBuzz::GetRunList() const {
   return const_cast<RenderTextHarfBuzz*>(this)->GetRunList();
 }
 
 }  // namespace gfx