Site-isolated frames from window.open should be able to navigate to the opener's domain
<rdar://problem/111064337>
Pull request: https://github.com/WebKit/WebKit/pull/19349
Committed 269622@main (825e39cd2f70): <https://commits.webkit.org/269622@main> Reviewed commits have been landed. Closing PR #19349 and removing active labels.