Async rendering will duplicate some of the code in UnifiedPDFPlugin::paintPDFContent(), so let's not duplicate more than we have to.
<rdar://problem/122851341>
Pull request: https://github.com/WebKit/WebKit/pull/24318
Committed 274552@main (6c12bd338a35): <https://commits.webkit.org/274552@main> Reviewed commits have been landed. Closing PR #24318 and removing active labels.