I forgot to add WTF_GUARDED_BY_LOCK.
<rdar://problem/105853141>
Pull request: https://github.com/WebKit/WebKit/pull/10617
Committed 260780@main (e2f6ecac142e): <https://commits.webkit.org/260780@main> Reviewed commits have been landed. Closing PR #10617 and removing active labels.