In intermediary state to bug 265982. We will put everything in place to be able to configure the MediaSourcePrivateRemote and SourceBufferPrivateRemote to run in a dedicated work queue. With the exception is that this dedicated work queue is currently the main thread.
<rdar://problem/119380172>
Pull request: https://github.com/WebKit/WebKit/pull/21507
Will directly go to bug 265982 *** This bug has been marked as a duplicate of bug 265982 ***