cc: Remove the base RasterSource

cc/layers/picture_layer_impl.h

Index: cc/layers/picture_layer_impl.h
diff --git a/cc/layers/picture_layer_impl.h b/cc/layers/picture_layer_impl.h
index 409afaeb9ca61d369bf70cdec6ef038c7202f08a..9cd7a215680954ef2b959ee96c29dcddef588404 100644
--- a/cc/layers/picture_layer_impl.h
+++ b/cc/layers/picture_layer_impl.h
@@ -66,7 +66,7 @@ class CC_EXPORT PictureLayerImpl
   void set_gpu_raster_max_texture_size(gfx::Size gpu_raster_max_texture_size) {
     gpu_raster_max_texture_size_ = gpu_raster_max_texture_size;
   }
-  void UpdateRasterSource(scoped_refptr<RasterSource> raster_source,
+  void UpdateRasterSource(scoped_refptr<DisplayListRasterSource> raster_source,
                           Region* new_invalidation,
                           const PictureLayerTilingSet* pending_set);
   bool UpdateTiles(bool resourceless_software_draw);
@@ -93,7 +93,9 @@ class CC_EXPORT PictureLayerImpl
   bool IsOnActiveOrPendingTree() const;
 
   // Used for benchmarking
-  RasterSource* GetRasterSource() const { return raster_source_.get(); }
+  DisplayListRasterSource* GetRasterSource() const {
+    return raster_source_.get();
+  }
 
  protected:
   friend class LayerRasterTileIterator;
@@ -132,7 +134,7 @@ class CC_EXPORT PictureLayerImpl
   PictureLayerImpl* twin_layer_;
 
   scoped_ptr<PictureLayerTilingSet> tilings_;
-  scoped_refptr<RasterSource> raster_source_;
+  scoped_refptr<DisplayListRasterSource> raster_source_;
   Region invalidation_;
 
   float ideal_page_scale_;