Upstream remaining compositing tests - most of them are basic and helped bringing up compositing in LBSE. All tests pass in LBSE already.
Pull request: https://github.com/WebKit/WebKit/pull/6291
Committed 256502@main (69d1edc2e196): <https://commits.webkit.org/256502@main> Reviewed commits have been landed. Closing PR #6291 and removing active labels.
<rdar://problem/102160180>