Fix crashes in GC creating a document fragment on a background thread
Created attachment 317069 [details] Patch
This regressed in r220095 (for bug https://webkit.org/b/175006).
Comment on attachment 317069 [details] Patch Clearing flags on attachment: 317069 Committed r220177: <http://trac.webkit.org/changeset/220177>
All reviewed patches have been landed. Closing bug.
<rdar://problem/33692758>