Remove the code which sorts and removes duplicates from the fallback font list

ui/gfx/render_text_harfbuzz.cc

Index: ui/gfx/render_text_harfbuzz.cc
diff --git a/ui/gfx/render_text_harfbuzz.cc b/ui/gfx/render_text_harfbuzz.cc
index 63b0e4e0cd79d009e83cb9989e680f987def1e06..2ade7510200be63e59909902129d4fe66a8a206d 100644
--- a/ui/gfx/render_text_harfbuzz.cc
+++ b/ui/gfx/render_text_harfbuzz.cc
@@ -5,6 +5,7 @@
 #include "ui/gfx/render_text_harfbuzz.h"
 
 #include <limits>
+#include <set>
 
 #include "base/i18n/bidi_line_iterator.h"
 #include "base/i18n/break_iterator.h"
@@ -467,6 +468,13 @@ class HarfBuzzLineBreaker {
   DISALLOW_COPY_AND_ASSIGN(HarfBuzzLineBreaker);
 };
 
+// Function object for case insensitive string comparison.
+struct CaseInsensitiveCompare {
+  bool operator() (const std::string& a, const std::string& b) const {
+    return base::strncasecmp(a.c_str(), b.c_str(), b.length()) < 0;

[msw, 2015/03/25 23:23:42]

Will strncasecmp work if a.length() != b.length()? Maybe use strcasecmp? 

[ananta, 2015/03/25 23:39:49]

It should. As per docs, it compares upto count characters and stops if
a NULL is seen in either string.

+  }
+};
+
 }  // namespace
 
 namespace internal {
@@ -1306,18 +1314,9 @@ void RenderTextHarfBuzz::ShapeRun(const base::string16& text,
   }
 #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());
+  // Use a set to track the fallback fonts and avoid duplicate entries.
+  std::set<std::string, CaseInsensitiveCompare>
+      duplicate_fallback_font_tracker;

[msw, 2015/03/25 23:23:42]

optional nit: rename |tried_fallback_fonts| or similar.

[ananta, 2015/03/25 23:39:49]

Renamed to duplicate_fallback_fonts

[msw, 2015/03/25 23:42:06]

Eh, they aren't duplicate themselves... the name |fallback_fonts| would be okay
with me, given the comment and simple usage.

 
   // Try shaping with the fallback fonts.
   for (const auto& family : fallback_families) {
@@ -1327,6 +1326,12 @@ void RenderTextHarfBuzz::ShapeRun(const base::string16& text,
     if (family == uniscribe_family)
       continue;
 #endif
+    if (duplicate_fallback_font_tracker.find(family) !=
+          duplicate_fallback_font_tracker.end())
+      continue;
+
+    duplicate_fallback_font_tracker.insert(family);
+
     FontRenderParamsQuery query(false);
     query.families.push_back(family);
     query.pixel_size = run->font_size;