This fixes several tests that were crashing (but not accounted for in gardening) in Debug builds when the track queues were being modified concurrently by separate threads.
Created attachment 317569 [details]
Created attachment 317570 [details]
Comment on attachment 317570 [details]
Clearing flags on attachment: 317570
Committed r220461: <http://trac.webkit.org/changeset/220461>
All reviewed patches have been landed. Closing bug.