As a follow up from https://bugs.webkit.org/show_bug.cgi?id=122321, if the region has overflow clip it should still paint over its positioned sibling because it is a stacking context.
Created attachment 213467 [details] Patch
Comment on attachment 213467 [details] Patch Nice catch, thanks!
Comment on attachment 213467 [details] Patch Clearing flags on attachment: 213467 Committed r157129: <http://trac.webkit.org/changeset/157129>
All reviewed patches have been landed. Closing bug.