Align our qualified name validation with the specification: - https://dom.spec.whatwg.org/#validate - https://www.w3.org/TR/xml/#NT-NameStartChar
Created attachment 378580 [details] Patch
Created attachment 378650 [details] Patch
Test failures seem real, or at least need re-baselining.
Created attachment 378668 [details] Patch
Comment on attachment 378668 [details] Patch r=me I'm skipping cq+ because this patch is a month old.
Created attachment 449524 [details] Patch
Committed r288264 (246206@main): <https://commits.webkit.org/246206@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 449524 [details].
<rdar://problem/87802929>