264920@main moved things around such that we no longer hit the WebCore "Schedule rendering update" trace point, so we need a new one in WebKit2.
<rdar://problem/111538471>
Pull request: https://github.com/WebKit/WebKit/pull/15425
Committed 265639@main (9a3acbde3c4b): <https://commits.webkit.org/265639@main> Reviewed commits have been landed. Closing PR #15425 and removing active labels.