Revert of cc: Remove tile sharing from tilings.

cc/resources/picture_layer_tiling_set.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_RESOURCES_PICTURE_LAYER_TILING_SET_H_
 #define CC_RESOURCES_PICTURE_LAYER_TILING_SET_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 161 matching lines @@
 
  private:
   explicit PictureLayerTilingSet(
       PictureLayerTilingClient* client,
       size_t max_tiles_for_interest_area,
       float skewport_target_time_in_seconds,
       int skewport_extrapolation_limit_in_content_pixels);
 
   void CopyTilingsAndPropertiesFromPendingTwin(
       const PictureLayerTilingSet* pending_twin_set,
-      const scoped_refptr<RasterSource>& raster_source,
-      const Region& layer_invalidation);
+      const scoped_refptr<RasterSource>& raster_source);
 
   // Remove one tiling.
   void Remove(PictureLayerTiling* tiling);
   void VerifyTilings(const PictureLayerTilingSet* pending_twin_set) const;
 
   ScopedPtrVector<PictureLayerTiling> tilings_;
 
   const size_t max_tiles_for_interest_area_;
   const float skewport_target_time_in_seconds_;
   const int skewport_extrapolation_limit_in_content_pixels_;
   PictureLayerTilingClient* client_;
 
   friend class Iterator;
   DISALLOW_COPY_AND_ASSIGN(PictureLayerTilingSet);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_LAYER_TILING_SET_H_