Add a PDF document "rendering" engine
Depends on D19251. Ref T13105. This adds rendering engine support for PDFs.
It doesn't actually render them, it just renders a link which you can click to view them in a new window. This is much easier than actually rendering them inline and at least 95% as good most of the time (and probably more-than-100%-as-good some of the time).
This makes PDF a viewable MIME type by default and adds a narrow CSP exception for it. See also T13112.
- Viewed PDFs in Files, got a link to view them in a new tab.
- Clicked the link in Safari, Chrome, and Firefox; got inline PDFs.
- Verified primary CSP is still object-src 'none' with curl ....
- Interacted with the vanilla lightbox element to check that it still works.
Maniphest Tasks: T13105
Differential Revision: https://secure.phabricator.com/D19252