Bug 40701: Improve security warning when downloading a file

Merge Info

• Related Issues

  • #40701 (closed)

• Backport Timeline

  • Immediate - patchsets for critical bug fixes or other major blocker (e.g. fixes for a 0-day exploit) OR patchsets with trivial changes which do not need testing (e.g. fixes for typos or fixes easily verified in a local developer build)
  • Next Minor Stable Release - patchset that needs to be verified in nightly before backport
  • Eventually - patchset that needs to be verified in alpha before backport
  • No Backport - patchset for the next major stable

• Upstream Merging

  • Merge to base-browser - typically for !fixups to patches in the base-browser branch, though sometimes new patches as well
    • NOTE: if your changeset includes patches to both base-browser and tor-browser please please make separate merge requests for each part

• Issue Tracking

  • Link resolved issues with appropriate Release Prep issue for changelog generation

Change Description

• Improve security warning when downloading a file
  • Flipping Always ask you where to save files and Ask whether to open or save files off by default to match Firefox.
  • Killing the existing "Download an external file type?" warning from torbutton
  • And adding a short warning to the Downloads wingpanel instead