Add a test to make sure the feature `verifyWindowOpenUserGestureFromUIProcess` works correctly when a mouse event is used to open a window.
<rdar://problem/119793659>
Pull request: https://github.com/WebKit/WebKit/pull/21949
Committed 272230@main (d7ea1558b098): <https://commits.webkit.org/272230@main> Reviewed commits have been landed. Closing PR #21949 and removing active labels.