Summary: While debugging something at Instagram, I kept seeing a UILabel be truncated when it clearly had enough room to display all its' text. What I realized is that during our pixel rounding, we were losing precision because we were using the incorrect rounding function for floats. Changing from `round()` (which is for doubles) to `roundf()` fixed it.
Reviewed By: amonshiz
Differential Revision: D4549069
fbshipit-source-id: 78a1bb33e315e7c066b7fb625b1f5a28def76515
