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

cc/layers/tiled_layer.h

Index: cc/layers/tiled_layer.h
diff --git a/cc/layers/tiled_layer.h b/cc/layers/tiled_layer.h
index 50e2b674f46d5209f76a9c06d29ffcfdea05711a..f2f7e96293f38632823ca6245ec8b09f59249ccc 100644
--- a/cc/layers/tiled_layer.h
+++ b/cc/layers/tiled_layer.h
@@ -46,7 +46,7 @@
   void UpdateBounds();
 
   // Exposed to subclasses for testing.
-  void SetTileSize(const gfx::Size& size);
+  void SetTileSize(gfx::Size size);
   void SetTextureFormat(ResourceFormat texture_format) {
     texture_format_ = texture_format;
   }