cc: Move tile sorting into separate function and add trace event.

cc/tile_manager.h

 // 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.
 
 #ifndef CC_TILE_MANAGER_H_
 #define CC_TILE_MANAGER_H_
 
 #include <list>
 #include <queue>
 #include <vector>
@@ skipping 80 matching lines @@
 
  protected:
   // Methods called by Tile
   friend class Tile;
   void RegisterTile(Tile* tile);
   void UnregisterTile(Tile* tile);
   void WillModifyTilePriority(
       Tile* tile, WhichTree tree, const TilePriority& new_priority);
 
  private:
+  void SortTiles();
   void AssignGpuMemoryToTiles();
   void FreeResourcesForTile(Tile* tile);
   void ScheduleManageTiles();
   void DispatchMoreTasks();
   void GatherPixelRefsForTile(Tile* tile);
   void DispatchImageDecodeTasksForTile(Tile* tile);
   void DispatchOneImageDecodeTask(
       scoped_refptr<Tile> tile, skia::LazyPixelRef* pixel_ref);
   void OnImageDecodeTaskCompleted(
       scoped_refptr<Tile> tile, uint32_t pixel_ref_id);
@@ skipping 28 matching lines @@
   TileQueue tiles_with_pending_set_pixels_;
 
   RenderingStats rendering_stats_;
 
   DISALLOW_COPY_AND_ASSIGN(TileManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILE_MANAGER_H_