[Mac] MSE-based video pauses when put in background; PiP context menu disabled
<rdar://78130303>
Created attachment 429028 [details] Patch
Created attachment 429034 [details] Patch
Created attachment 429050 [details] Patch for landing
Committed r277726 (237903@main): <https://commits.webkit.org/237903@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 429050 [details].