RunLoop Observers support `breakToAllowRenderingUpdate()`, which lets us schedule a rendering update to happen without waiting for other tasks.
Pull request: https://github.com/WebKit/WebKit/pull/13013
Committed 263269@main (465af8bb6a56): <https://commits.webkit.org/263269@main> Reviewed commits have been landed. Closing PR #13013 and removing active labels.
<rdar://problem/108390477>
Re-opened since this is blocked by bug 255851
Pull request: https://github.com/WebKit/WebKit/pull/13166