Currently we paint highlight synchronously upon scroll. Putting it into the setTimeout makes scrolling really smooth, while highlight becomes available upon scroll finish.
Created attachment 48817 [details] [PATCH] Proposed change.
Comment on attachment 48817 [details] [PATCH] Proposed change. Clearing flags on attachment: 48817 Committed r54871: <http://trac.webkit.org/changeset/54871>
All reviewed patches have been landed. Closing bug.