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

cc/trees/occlusion_tracker.h

Index: cc/trees/occlusion_tracker.h
diff --git a/cc/trees/occlusion_tracker.h b/cc/trees/occlusion_tracker.h
index 85334bca2c19ec304bd4268b2801046103f01e1c..2fe54d009765cda20fc0eebd3d9ca46c34c3bfad 100644
--- a/cc/trees/occlusion_tracker.h
+++ b/cc/trees/occlusion_tracker.h
@@ -82,7 +82,7 @@ class CC_EXPORT OcclusionTrackerBase {
                            stack_.back().occlusion_from_inside_target);
   }
 
-  void set_minimum_tracking_size(gfx::Size size) {
+  void set_minimum_tracking_size(const gfx::Size& size) {
     minimum_tracking_size_ = size;
   }