Safari 6.0.5 draws blurry patches with latest renderer. other browsers fine

Safari 6.0.5, Mac OS X 10.8.5:

![screen shot 2013-10-21 at 7 33 41 pm](https://f.cloud.github.com/assets/161079/1377527/6a44880a-3aa9-11e3-8950-ee41f14225e2.png)