The chunked update drawing area is flipped twice when drawing
Created attachment 75514 [details]
Comment on attachment 75514 [details]
I think you can save on a bunch of function calls here. Roll the translation into the origin of the parameter you pass to CGContextDrawImage, and instead of saving and restoring gstate, just apply the scale again.
Committed r73275: <http://trac.webkit.org/changeset/73275>