Leverage isASCIILower() / toASCIILower() in the new HTML parsing fast path.
Pull request: https://github.com/WebKit/WebKit/pull/10001
Committed 260170@main (74372cf946b0): <https://commits.webkit.org/260170@main> Reviewed commits have been landed. Closing PR #10001 and removing active labels.
<rdar://problem/105368774>