cc: Use multiple PrepareTiles approaches

cc/tiles/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_TILES_PICTURE_LAYER_TILING_H_
 #define CC_TILES_PICTURE_LAYER_TILING_H_
 
 #include <map>
 #include <utility>
 #include <vector>
@@ skipping 92 matching lines @@
       int skewport_extrapolation_limit_in_content_pixels);
 
   void SetRasterSourceAndResize(scoped_refptr<RasterSource> raster_source);
   void Invalidate(const Region& layer_invalidation);
   void CreateMissingTilesInLiveTilesRect();
   void TakeTilesAndPropertiesFrom(PictureLayerTiling* pending_twin,
                                   const Region& layer_invalidation);
 
   bool IsTileRequiredForActivation(const Tile* tile) const;
   bool IsTileRequiredForDraw(const Tile* tile) const;
+  bool RasterSourceCoversCurrentVisibleTiles() const;
 
   void set_resolution(TileResolution resolution) { resolution_ = resolution; }
   TileResolution resolution() const { return resolution_; }
   void set_can_require_tiles_for_activation(bool can_require_tiles) {
     can_require_tiles_for_activation_ = can_require_tiles;
   }
 
   RasterSource* raster_source() const { return raster_source_.get(); }
   gfx::Size tiling_size() const { return tiling_data_.tiling_size(); }
   gfx::Rect live_tiles_rect() const { return live_tiles_rect_; }
@@ skipping 273 matching lines @@
 
  private:
   DISALLOW_ASSIGN(PictureLayerTiling);
 
   RectExpansionCache expansion_cache_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_PICTURE_LAYER_TILING_H_