This is only used by Qt so far and only enabled when you have the tiling enabled.
Created attachment 73234 [details] Patch
Comment on attachment 73234 [details] Patch r=me
Comment on attachment 73234 [details] Patch Clearing flags on attachment: 73234 Committed r71600: <http://trac.webkit.org/changeset/71600>
All reviewed patches have been landed. Closing bug.