This is a uncaught "bug" from r192705 (https://bugs.webkit.org/show_bug.cgi?id=150494).
<rdar://problem/24032171>
Created attachment 268113 [details] Patch
Comment on attachment 268113 [details] Patch Clearing flags on attachment: 268113 Committed r194539: <http://trac.webkit.org/changeset/194539>
All reviewed patches have been landed. Closing bug.