cc: Generate tilings at other scales for impl-side painting

cc/picture_layer_impl.h

Index: cc/picture_layer_impl.h
diff --git a/cc/picture_layer_impl.h b/cc/picture_layer_impl.h
index 94c1ac31b36a29c26cff34d860a7984e03dc3b07..1712b4433146ec934a25290ba4289562d0ee6b15 100644
--- a/cc/picture_layer_impl.h
+++ b/cc/picture_layer_impl.h
@@ -53,10 +53,11 @@ public:
 
 protected:
   PictureLayerImpl(LayerTreeImpl* treeImpl, int id);
-  void AddTiling(float contents_scale, gfx::Size tile_size);
+  PictureLayerTiling* AddTiling(float contents_scale);
   void SyncFromActiveLayer(const PictureLayerImpl* other);
   gfx::Size TileSize() const;
   void ManageTilings(float ideal_contents_scale);
+  void CleanUpUnusedTilings(std::vector<PictureLayerTiling*> used_tilings);
 
   PictureLayerTilingSet tilings_;
   scoped_refptr<PicturePileImpl> pile_;
@@ -66,8 +67,8 @@ protected:
   double last_update_time_;
   gfx::Size last_bounds_;
   gfx::Size last_content_bounds_;
-  float last_content_scale_x_;
-  float last_content_scale_y_;
+  float last_content_scale_;
+  float ideal_contents_scale_;
   bool is_mask_;
 
   friend class PictureLayer;