:lang() selectors should serialize without quotation marks if they were parsed without them WPT tests make this clear, and while there is nothing obvious in the specification that explicitly calls for this, it does make logical sense. There is a relatively straightforward way to do this in the short term.
<rdar://problem/102198822>
Pull request: https://github.com/WebKit/WebKit/pull/6359
Committed 256603@main (7e31f273a4e1): <https://commits.webkit.org/256603@main> Reviewed commits have been landed. Closing PR #6359 and removing active labels.