Audio/video player is blank in 6.5a2
[A blog commenter writes](https://blog.torproject.org/blog/tor-browser-65a2-released#comment-196694):
Previous builds would have a dark background with simple controls for video or audio playback. There are no longer visible controls for video/audio, just a blank white background, and I cannot view statistics or seek. Same behavior from local files [mp3/4].
I can reproduce this. The player plays but there are no controls; in the case of an audio file this means the whole page is blank. It works as expected in 6.0.3.
Try these example URLs:
https://archive.org/download/OrsonWellesMrBruns/381030.ogg (audio)
https://extra.torproject.org/blog/2016-08-PT-animation/pluggable_transports-animation.mp4 (video)
Here is how the audio player looks in 6.0.3:

And in 6.5a2 it's just blank:

issue