[#7] Pass gfx structs by const ref (gfx::Size)

cc/resources/layer_updater.h

Index: cc/resources/layer_updater.h
diff --git a/cc/resources/layer_updater.h b/cc/resources/layer_updater.h
index 730773f56e0a9710925171f4d9745f80d03a0863..d12d7b4b35e577a39844911c8ca339f2efef4462 100644
--- a/cc/resources/layer_updater.h
+++ b/cc/resources/layer_updater.h
@@ -49,7 +49,7 @@ class CC_EXPORT LayerUpdater : public base::RefCounted<LayerUpdater> {
   // painted opaque. If the layer is marked opaque in the updater, then this
   // region should be ignored in preference for the entire layer's area.
   virtual void PrepareToUpdate(const gfx::Rect& content_rect,
-                               gfx::Size tile_size,
+                               const gfx::Size& tile_size,
                                float contents_width_scale,
                                float contents_height_scale,
                                gfx::Rect* resulting_opaque_rect) {}