cc: Update picture pile on tiles to prevent memory leak

cc/picture_layer_tiling.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_PICTURE_LAYER_TILING_H_
 #define CC_PICTURE_LAYER_TILING_H_
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/cc_export.h"
 #include "cc/hash_pair.h"
 #include "cc/region.h"
 #include "cc/tile.h"
 #include "cc/tile_priority.h"
 #include "cc/tiling_data.h"
 #include "ui/gfx/rect.h"
 
 namespace cc {
 
 class PictureLayerTiling;
 
 class PictureLayerTilingClient {
   public:
    virtual scoped_refptr<Tile> CreateTile(PictureLayerTiling*, gfx::Rect) = 0;
+   virtual void UpdatePile(Tile* tile) = 0;
 };
 
 class CC_EXPORT PictureLayerTiling {
  public:
   ~PictureLayerTiling();
 
   static scoped_ptr<PictureLayerTiling> Create(float contents_scale,
                                                gfx::Size tile_size);
   scoped_ptr<PictureLayerTiling> Clone() const;
 
@@ skipping 58 matching lines @@
 
   void UpdateTilePriorities(
       WhichTree tree,
       const gfx::Size& device_viewport,
       float last_contents_scale,
       float current_contents_scale,
       const gfx::Transform& last_screen_transform,
       const gfx::Transform& current_screen_transform,
       double time_delta);
 
-  void MoveTilePriorities(WhichTree src_tree, WhichTree dst_tree);
+  // Copies the src_tree priority into the dst_tree priority for all tiles.
+  // The src_tree priority is reset to the lowest priority possible.  This
+  // also updates the pile on each tile to be the current client's pile.
+  void DidBecomeActive();
 
  protected:
   typedef std::pair<int, int> TileMapKey;
   typedef base::hash_map<TileMapKey, scoped_refptr<Tile> > TileMap;
 
   PictureLayerTiling(float contents_scale, gfx::Size tileSize);
   Tile* TileAt(int, int) const;
   void CreateTile(int i, int j);
 
   PictureLayerTilingClient* client_;
   float contents_scale_;
   gfx::Size layer_bounds_;
   TileMap tiles_;
   TilingData tiling_data_;
   TileResolution resolution_;
 
   friend class Iterator;
 };
 
 }  // namespace cc
 
 #endif  // CC_PICTURE_LAYER_TILING_H_