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

cc/resources/picture_pile.cc

 // Copyright 2012 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 "cc/resources/picture_pile.h"
 
 #include <algorithm>
 #include <limits>
 #include <vector>
 
@@ skipping 98 matching lines @@
   std::vector<gfx::Rect> invalid_tiles_vertical = invalid_tiles;
   std::sort(invalid_tiles_vertical.begin(),
             invalid_tiles_vertical.end(),
             rect_sort_y);
 
   float vertical_density;
   std::vector<gfx::Rect> vertical_clustering;
   vertical_density = PerformClustering(invalid_tiles_vertical,
                                        &vertical_clustering);
 
+  // If vertical density is optimal, then we can return early.
+  if (vertical_density == 1.f) {
+    *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;
-  std::sort(invalid_tiles_vertical.begin(),
-            invalid_tiles_vertical.end(),
+  std::sort(invalid_tiles_horizontal.begin(),
+            invalid_tiles_horizontal.end(),
             rect_sort_x);
 
   float horizontal_density;
   std::vector<gfx::Rect> horizontal_clustering;
-  horizontal_density = PerformClustering(invalid_tiles_vertical,
+  horizontal_density = PerformClustering(invalid_tiles_horizontal,
                                          &horizontal_clustering);
 
   if (vertical_density < horizontal_density) {
     *record_rects = horizontal_clustering;
     return horizontal_density;
   }
 
   *record_rects = vertical_clustering;
   return vertical_density;
 }
@@ skipping 165 matching lines @@
     }
     DCHECK(found_tile_for_recorded_picture);
   }
 
   has_any_recordings_ = true;
   DCHECK(CanRasterSlowTileCheck(recorded_viewport_));
   return true;
 }
 
 }  // namespace cc