https://w3c.github.io/csswg-drafts/css-box-4/#margin-trim-block
<rdar://problem/105984917>
Pull request: https://github.com/WebKit/WebKit/pull/10765
Committed 260950@main (bad6e12c6625): <https://commits.webkit.org/260950@main> Reviewed commits have been landed. Closing PR #10765 and removing active labels.