[UI-side compositing] Scrollbar tests should use web process state for select elements
<rdar://problem/108275933>
Pull request: https://github.com/WebKit/WebKit/pull/12925
Committed 263656@main (db42544a3d68): <https://commits.webkit.org/263656@main> Reviewed commits have been landed. Closing PR #12925 and removing active labels.