FWIW, these aren&#x27;t actually enabled in 46 unless you flip the `layout.css.prefixes.webkit` pref to true.<p>(We hope to flip that to true by default soon: <a href="https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1259345" rel="nofollow">https:&#x2F;&#x2F;bugzilla.mozilla.org&#x2F;show_bug.cgi?id=1259345</a>)