Attached testcase shows a problem where elements with subpixel offsets don't paint the right/bottom line of pixels when in compositing layers.
This causes an appearance change when toggling compositing on an element.
Created attachment 234033 [details]
Created attachment 234034 [details]
Comment on attachment 234034 [details]
Clearing flags on attachment: 234034
Committed r170563: <http://trac.webkit.org/changeset/170563>
All reviewed patches have been landed. Closing bug.