'rem' unit and others can create property cycles that apply to the document element style only.
<rdar://problem/104324136>
Pull request: https://github.com/WebKit/WebKit/pull/8714
Committed 258985@main (c3229c227bf8): <https://commits.webkit.org/258985@main> Reviewed commits have been landed. Closing PR #8714 and removing active labels.