Tor Browser cannot print to file

This regression was introduced in Tails 3.3 when that imports Tor Browser 7.0.10-build2.

When printing to file it looks like it succeeds (dialog’s progress goes to 100%, no errors are shown) but the file is not created, and I can see this written to the journal:

Dec 08 13:49:50 amnesia firefox[12397]: /build/glib2.0-2.50.3/./gobject/gsignal.c:3492: signal name 'selection_changed' is invalid for instance '0x7dd7c1dc2740' of type 'MaiAtkType319'

Note:

• the above journal error is not emitted when printing in Tor Browser in Tails 3.2,
• but it is also emitted in Tails 3.3 when printing with a real printer too, and that works

Feature Branch: feature/15197-tor-browser-7.5

Related issues

• Related to #13403 (closed)
• Related to #15336
• Has duplicate #14978 (closed)
• Has duplicate #15066 (closed)
• Blocks #13245 (closed)
• Blocked by #15197 (closed)

Original created by @anonym on 15024 (Redmine)