Undo some of 268697@main so that the UnifiedPDFPlugin once again is a fixed size; in future, it will scroll internally as the PDFPlugin does.
<rdar://problem/116609170>
Pull request: https://github.com/WebKit/WebKit/pull/18803
Committed 269048@main (b4ec9b506ed2): <https://commits.webkit.org/269048@main> Reviewed commits have been landed. Closing PR #18803 and removing active labels.