In beta.brie.fi/ng, clicking on a participant's stream to make it fill the window does not work

[jmbreuer]

As opposed to stable brie.fi/ng, in the beta version, clicking on the other participant's stream does not make their stream cover most of my window, with my own video shrinking to a preview overlay in the corner.

(In non-beta, I can also enlarge my own stream by clicking on it from the 'democratic' view where all streams are shown equal size.)

Is this a not-yet-implemented/missing feature, is it supposed to work but broken for me for some reason, or is it supposed to be accessed/triggered in a different way that I haven't found?