c:: Give the raster source to the PictureLayerTilings.

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 ed98434578f9606261a8d37130d9f54124baa167..718c0cfff08ee530bb61feae440f7879555eb560 100644
--- a/cc/layers/picture_layer_impl.h
+++ b/cc/layers/picture_layer_impl.h
@@ -68,7 +68,7 @@ class CC_EXPORT PictureLayerImpl
   skia::RefPtr<SkPicture> GetPicture() override;
 
   // PictureLayerTilingClient overrides.
-  scoped_refptr<Tile> CreateTile(PictureLayerTiling* tiling,
+  scoped_refptr<Tile> CreateTile(float contents_scale,
                                  const gfx::Rect& content_rect) override;
   gfx::Size CalculateTileSize(const gfx::Size& content_bounds) const override;
   const Region* GetPendingInvalidation() override;
@@ -105,7 +105,7 @@ class CC_EXPORT PictureLayerImpl
   bool AllTilesRequiredForDrawAreReadyToDraw() const;
 
   // Used for benchmarking
-  const RasterSource* GetRasterSource() const { return raster_source_.get(); }
+  RasterSource* GetRasterSource() const { return raster_source_.get(); }
 
  protected:
   friend class LayerRasterTileIterator;