Improve UX of saving downloaded files and pages to PDF from Tor Browser

This is a parent issue for the whole problem. See below for child and related issues.

Solutions

• Grant Tor Browser access to files as designated... (#10422) would be the ideal solution, but it seems like it will still take years to get there.
• Remove the `tor-browser` shortcut from the side... (#19254) would remove part of the confusion and is needed even with #10422.
• Rename "Tor Browser" shortcuts and folders as "... (#15028) would orient people better to a folder where they can actually save something
• Remove default folders from Home and sidebar (#10790) would limit the number of shortcuts where people can't actually save anything
• Allow Tor Browser to save files to Documents, D... (#19255) could temporarily lift a bit of this UX regression
• Improve the language of the error message to provide guidance?
  • Is this message possible to customize?

Print → Save to PDF

Reported by @cbrownstein on #18915 (closed):

In Tor Browser: ☰ ▸ Print… ▸ Save to PDF silently fails when in default directory

Help Desk has received reports about this issue and I'm able to replicate it.

In Tor Browser, selecting ☰ ▸ Print… ▸ Save to PDF silently fails when the directory is not changed from the default. The default directory is /usr/local/lib/tor-browser/.

This behavior also occurs if Print using the system dialog… ▸ Print to file is selected.

I'm sure that users expect the default directory to be a writable directory.

User research findings

• During #18648 (closed), all of the 4 participants failed to save an image without help.

• During the user testing of the VeraCrypt beta in 2018, participants had to save a keyfile from Tor Browser and use it to unlock a USB stick:

  • 2 participants saved it to ~/Tor Browser without problems.
  • The other 3 participants had a very hard time finding how to save it:
    • It took P2 2 minutes to find where it was possible to save it. He even tried “~/Tor Browser/” without realizing it would work and went ahead checking more folders.
    • P3 dismissed the error message and saved it to the desktop but it was not save. Then she couldn’t find it.
    • P4 has an odyssey of 8 minutes and was unsuccessfully looking for her file under /usr/local/lib/tor-browser/ when I rescued her.

  Some user quotes:

  • P3: « I don’t want to read. I want to save. » after getting the error message “Could not read the content of …”
  • P4: « I don’t have permission to save anywhere. It’s fucking useless. »
  • P4: « Why am I using a computer I don’t have permissions to use. »
  • P4: « This is fucking kafkaesque… »