The following functions should be aligned with regards to validating bound VAOs (if needed), doing implicit clears, and marking the canvas as changed.
See also similar Chromium-side bug http://crbug.com/1333620 .
I think this tests the compositing implications
Committed r295486 (251491@main): <https://commits.webkit.org/251491@main>
Reviewed commits have been landed. Closing PR #1452 and removing active labels.