sub-task of bug 264134. dependent on bug 264847 which introduced NativePromise in MSE code.
<rdar://problem/118429088>
Pull request: https://github.com/WebKit/WebKit/pull/20516
Committed 270808@main (19836c74aa9f): <https://commits.webkit.org/270808@main> Reviewed commits have been landed. Closing PR #20516 and removing active labels.