Created attachment 256275 [details] Animated GIF of the problem :(
<rdar://problem/21698973>
Created attachment 256278 [details] Patch
Tried the patch, it fixed the issue for me.
Comment on attachment 256278 [details] Patch Clearing flags on attachment: 256278 Committed r186463: <http://trac.webkit.org/changeset/186463>
All reviewed patches have been landed. Closing bug.