cc: Move raster_source from Tile to PrioritizedTile

cc/resources/prioritized_tile.h

 // Copyright 2015 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_RESOURCES_PRIORITIZED_TILE_H_
 #define CC_RESOURCES_PRIORITIZED_TILE_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/resources/tile.h"
 #include "cc/resources/tile_priority.h"
 
 namespace cc {
 class PictureLayerTiling;
+class RasterSource;
 
 class CC_EXPORT PrioritizedTile {
  public:
   // This class is constructed and returned by a |PictureLayerTiling|, and
   // represents a tile and its priority.
   PrioritizedTile();
   ~PrioritizedTile();
 
   Tile* tile() const { return tile_; }
+  RasterSource* raster_source() const { return raster_source_; }
   const TilePriority& priority() const { return priority_; }
   bool is_occluded() const { return is_occluded_; }
 
  private:
   friend class PictureLayerTiling;
 
-  PrioritizedTile(Tile* tile, const TilePriority priority, bool is_occluded);
+  PrioritizedTile(Tile* tile,
+                  RasterSource* raster_source,
+                  const TilePriority priority,
+                  bool is_occluded);
 
   Tile* tile_;
+  RasterSource* raster_source_;
   TilePriority priority_;
   bool is_occluded_;
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PRIORITIZED_TILE_H_