PDF.js automatically opens a sidebar for large documents, we don't want it.
<rdar://problem/89157217>
I think we can do this from the content-script: removing the sidebarOpen class from #outerContainer.
Created attachment 452879 [details] [fast-cq] Patch
Committed r290321 (247643@main): <https://commits.webkit.org/247643@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 452879 [details].