HTMLToken::beginStartTag is only ever called with an ASCII lowercase letter. It can take an LChar instead of a UChar, and we can avoid updating m_data8BitCheck.
Created attachment 451203 [details] Patch
Committed r289410 (246977@main): <https://commits.webkit.org/246977@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 451203 [details].
<rdar://problem/88642964>