We currently crash when viewing a page with a PlaceholderRenderingContext. I don't know if we can support recording as such, since this context type isn't exposed to JS (and doesn't do any drawing as such, it just gets an image set each frame).
Pull request: https://github.com/WebKit/WebKit/pull/13999
Committed 264225@main (3d5cd5c1bfd1): <https://commits.webkit.org/264225@main> Reviewed commits have been landed. Closing PR #13999 and removing active labels.
<rdar://problem/109539709>