Images are cropped in new messaging UI, videos are small

Something in new messaging interface CSS tries to squish the contents of the messages. It is especially obvious when you try to send somebody an image or a video. Video.js player in Moodle uses "fluid" layout where videos are automatically resized to 100% of their container width to ensure responsiveness (there is also max-width specified so they don't get too wide).

Probably the easiest way to see what's going on is to try to send somebody an image (I used https://www.ancestry.com/wiki/images/archive/a/a9/20100708215937!Example.jpg ).

1. Enable url-to-link and multimedia filter (urltolink first)
2. Open messaging window and try to send somebody a url to an image or a video file, for example https://www.ancestry.com/wiki/images/archive/a/a9/20100708215937!Example.jpg or http://techslides.com/demos/sample-videos/small.mp4
3. try to do the same but with the text in the same message