[#2] Pass gfx structs by const ref (gfx::Rect, gfx::RectF)

cc/resources/tile.h

Index: cc/resources/tile.h
diff --git a/cc/resources/tile.h b/cc/resources/tile.h
index 548d9c985c4ebccd8f0d468022c9e3eb1058fce3..32e66518b0f5c084ea5bef4795bf9974e76150c8 100644
--- a/cc/resources/tile.h
+++ b/cc/resources/tile.h
@@ -133,8 +133,8 @@ class CC_EXPORT Tile : public RefCountedManaged<Tile> {
   Tile(TileManager* tile_manager,
        PicturePileImpl* picture_pile,
        gfx::Size tile_size,
-       gfx::Rect content_rect,
-       gfx::Rect opaque_rect,
+       const gfx::Rect& content_rect,
+       const gfx::Rect& opaque_rect,
        float contents_scale,
        int layer_id,
        int source_frame_number,