Currently, we update non compositing layer when the page scrolled. However, it is not needed, because TiledBackingStore can scroll without tile update.
Created attachment 189485 [details] Patch
Comment on attachment 189485 [details] Patch LGTM, please ping WK2 owners.
Comment on attachment 189485 [details] Patch Sure, I sign off on this.
Comment on attachment 189485 [details] Patch Clearing flags on attachment: 189485 Committed r144012: <http://trac.webkit.org/changeset/144012>
All reviewed patches have been landed. Closing bug.