It is deprecated and all newer rule types should return 0. "This enumeration is thus frozen in its current state, and no new new values will be added to reflect additional at-rules; all at-rules beyond the ones listed above will return 0." https://w3c.github.io/csswg-drafts/cssom/#the-cssrule-interface
<rdar://problem/103531316>
Pull request: https://github.com/WebKit/WebKit/pull/7874
Committed 258128@main (f34b82d5e7cb): <https://commits.webkit.org/258128@main> Reviewed commits have been landed. Closing PR #7874 and removing active labels.
Reverted by https://github.com/WebKit/WebKit/pull/7909
Committed 258132@main (ef048420b599): <https://commits.webkit.org/258132@main> Reviewed commits have been landed. Closing PR #7910 and removing active labels.
Reverted by https://github.com/WebKit/WebKit/pull/7912
Committed 258135@main (b961cddcf858): <https://commits.webkit.org/258135@main> Reviewed commits have been landed. Closing PR #7912 and removing active labels.