See: https://bugs.webkit.org/show_bug.cgi?id=172003. I didn't check but I would guess this is also true for bmalloc too.
<rdar://problem/32495975>
Whoops, the bugzilla should be https://bugs.webkit.org/show_bug.cgi?id=172775.
I see the problem.
Created attachment 311674 [details] proposed fix
Comment on attachment 311674 [details] proposed fix good catch.
Comment on attachment 311674 [details] proposed fix Clearing flags on attachment: 311674 Committed r217646: <http://trac.webkit.org/changeset/217646>
All reviewed patches have been landed. Closing bug.