It is useful in combination with content-visibility.
https://drafts.csswg.org/cssom-view/#extension-to-the-element-interface
<rdar://problem/117113659>
Pull request: https://github.com/WebKit/WebKit/pull/19210
Committed 269506@main (7d04a9c1b62b): <https://commits.webkit.org/269506@main> Reviewed commits have been landed. Closing PR #19210 and removing active labels.