[Cocoa] ::cue background-color not changed unless "allow video to override" unchecked
<rdar://problem/112100260>
Pull request: https://github.com/WebKit/WebKit/pull/15752
Committed 265975@main (bb909a833152): <https://commits.webkit.org/265975@main> Reviewed commits have been landed. Closing PR #15752 and removing active labels.