cc: skipping a horizontal sort by checking the value of vertical_density

cc/resources/picture_pile.cc

Index: cc/resources/picture_pile.cc
diff --git a/cc/resources/picture_pile.cc b/cc/resources/picture_pile.cc
index 6341e88b3688889df468543cecf2c652136f20c9..9991b13753872320a650a5c7bfb9c4ceb9d0b6c3 100644
--- a/cc/resources/picture_pile.cc
+++ b/cc/resources/picture_pile.cc
@@ -116,8 +116,12 @@ float ClusterTiles(const std::vector<gfx::Rect>& invalid_tiles,
   vertical_density = do_clustering(invalid_tiles_vertical,
                                    &vertical_clustering);
 
+  if (vertical_density == 1) {

[vmpstr, 2014/07/09 23:29:11]

nit: 1.f

[hyunki, 2014/07/09 23:43:44]

Done.

+    *record_rects = vertical_clustering;
+    return vertical_density;
+  }
+
   // Now try again with a horizontal sort, see which one is best
-  // TODO(humper): Heuristics for skipping this step?
   std::vector<gfx::Rect> invalid_tiles_horizontal = invalid_tiles;

[vmpstr, 2014/07/09 23:29:11]

Is this used? I think this might have been a typo, but can you fix that while
you're here? And possibly rename invalid_tiles_vertical to something like
invalid_tiles_copy. Either that or use invalid_tiles_horizontal below, whichever
is more efficient.

[hyunki, 2014/07/09 23:43:44]

Sure. I think it is used.
And possibly rename invalid_tiles_vertical to something like
I have changed it to invalid_tiles_horizontal.

Done.

   std::sort(invalid_tiles_vertical.begin(),
             invalid_tiles_vertical.end(),