Fix leak of AVPlayer boundaryTimeObserver object.
<rdar://problem/46706335>
Created attachment 357246 [details] Patch
<rdar://problem/46706345>
Comment on attachment 357246 [details] Patch Clearing flags on attachment: 357246 Committed r239180: <https://trac.webkit.org/changeset/239180>
All reviewed patches have been landed. Closing bug.