Correct handling for vertical writing mode per https://github.com/w3c/csswg-drafts/issues/6873
<rdar://problem/111565488>
Pull request: https://github.com/WebKit/WebKit/pull/15443
Committed 265654@main (b4d32d728a61): <https://commits.webkit.org/265654@main> Reviewed commits have been landed. Closing PR #15443 and removing active labels.