For reasons not totally clear to me, Github marked #4160 as "merged" and
will not let me reopen it.
I believe this should be included for 24.1 because it fixes a 24.0
regression in the media player.
I have tested this newest commit in a number of ways, and in my testing
I find (1) when viewing an image, it sleeps after about a minute (2)
when viewing video, it stays awake indefinitely (3) this is true whether
the image/video was opened directly, or reached by swiping from another
attachment. I have not tested swiping to/from audio but I am confident
it will work the same.
331b13621e