Canvas data extraction should be allowed when *local* pdf.js is invoked

[cypherpunks]

How to reproduce the issue:

(1) Go to the following URL: https://web.archive.org/web/20180211235741/https://research.torproject.org/techreports/tbb-forensic-analysis-2013-06-28.pdf

(2) Click on the "Toggle Sidebar" button, as in here:

(3) The thumbnails are empty, and in the browser console: Blocked https://web.archive.org/web/20180211235741if_/https://research.torproject.org/techreports/tbb-forensic-analysis-2013-06-28.pdf in page https://web.archive.org/web/20180211235741/https://research.torproject.org/techreports/tbb-forensic-analysis-2013-06-28.pdf from extracting canvas data. resource://pdf.js/web/viewer.js:3311.

Note that it's the local resource://pdf.js/web/viewer.js that is invoked and not some bundled pdf.js.

[tom]

This maybe (hopefully) corresponds to ​https://bugzilla.mozilla.org/show_bug.cgi?id=1412961

In 60, my hope is that fixing this will fix that one also.

[cypherpunks]

This can also be solved with #24521 but I don't see it being resolved in the near term.

[cypherpunks]

tom:

In 60, my hope is that fixing this will fix that one also.

[cypherpunks]

Unfortunately the ticket linked by Tom was fixed on 61, backport maybe? (I'm encountering this bug with TB 8.0a9 FWIW)

[gk]

Replying to cypherpunks:

Unfortunately the ticket linked by Tom was fixed on 61, backport maybe? (I'm encountering this bug with TB 8.0a9 FWIW)

Actually, we'd need the fix for ​https://bugzilla.mozilla.org/show_bug.cgi?id=1453916 as well. So, hrm.

[gk]

We could test and backport the patches that landed in Firefox 61?