When clicking on a link to an .mp4 file, Firefox navigates to a builtin video player, streaming the remote video file. When Firefox is unable to stream or display a file (as is the case with .mkv or .txt for example), it is downloaded instead.

I simply want .mp4 files to be downloaded when I navigate to them. I tried setting `media.mp4.enabled` to `false`, and that worked, but it also disabled most embedded media players.