This will be a nicer fix to bug 228740. We could use a WTF::Observer to notify clients that the PiP/FullScreen state has changed without having to worry about set/clearing clients.
<rdar://problem/81489026>
Created attachment 434884 [details] Patch
Committed r280670 (240275@main): <https://commits.webkit.org/240275@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 434884 [details].