This test does not seem to be spec-conformant (beforeunload alerts should be dismissed automatically), but it shouldn't hang either.
<rdar://problem/41909520>
Created attachment 344467 [details] Patch
Comment on attachment 344467 [details] Patch Clearing flags on attachment: 344467 Committed r233600: <https://trac.webkit.org/changeset/233600>
All reviewed patches have been landed. Closing bug.
Committed r233641: <https://trac.webkit.org/changeset/233641>