https://drafts.csswg.org/css-contain-3/#container-queries "Style rules applying to its shadow-including descendants can then be conditioned by querying against it, using the @container conditional group rule."
Created attachment 456922 [details] Patch
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/33552
This patch modifies the imported WPT tests. Please ensure that any changes on the tests (not coming from a WPT import) are exported to WPT. Please see https://trac.webkit.org/wiki/WPTExportProcess
Comment on attachment 456922 [details] Patch r=me if EWS is ok with it
Committed r292592 (249425@main): <https://commits.webkit.org/249425@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 456922 [details].
<rdar://problem/91463362>