It should be possible to use WTF::CallbackAggregator from a background thread. John needs it for ITP code which lives on a background queue. The CallbackAggregator destructor currently always calls the CompletionHandler on the main thread no matter what.
Created attachment 345889 [details]
Comment on attachment 345889 [details]
Clearing flags on attachment: 345889
Committed r234288: <https://trac.webkit.org/changeset/234288>
All reviewed patches have been landed. Closing bug.