We don't support this currently in the UnifiedPDFPlugin. Let's fix that.
<rdar://problem/122672464>
Pull request: https://github.com/WebKit/WebKit/pull/24181
Committed 274430@main (55e6e1431a97): <https://commits.webkit.org/274430@main> Reviewed commits have been landed. Closing PR #24181 and removing active labels.