Re-land r262863
Created attachment 402891 [details] Patch
Comment on attachment 402891 [details] Patch r=me. You might also want to remove RunLoop::mainIfExists that I added in r263524.
Bokay!
Created attachment 402896 [details] Patch for landing
Committed r263580: <https://trac.webkit.org/changeset/263580> All reviewed patches have been landed. Closing bug and clearing flags on attachment 402896 [details].
<rdar://problem/64820693>
<rdar://problem/64820696>