There is a bug whereby disconnecting a subtree with a lang content attribute makes :lang pseudo class to never match a descendant of an element with the lang content attribute.
Pull request: https://github.com/WebKit/WebKit/pull/3764
<rdar://problem/99268632>
Committed 253915@main (06479a26a2b9): <https://commits.webkit.org/253915@main> Reviewed commits have been landed. Closing PR #3764 and removing active labels.