This is necessary in order to support vertical writing modes and flipped block directions.
<rdar://problem/115965535>
Pull request: https://github.com/WebKit/WebKit/pull/18138
Committed 268414@main (9aea0cafc6c8): <https://commits.webkit.org/268414@main> Reviewed commits have been landed. Closing PR #18138 and removing active labels.