With render trees gone from the page cache, we don't have to worry about custom scrollbars in CachedFrame since they are already nuked by the render tree teardown.
Created attachment 300902 [details] Patch
Comment on attachment 300902 [details] Patch Clearing flags on attachment: 300902 Committed r211885: <http://trac.webkit.org/changeset/211885>
All reviewed patches have been landed. Closing bug.