Contributed by Nils Ohlmeier, Hacking on real time communications since 2002
Until very recently you had to be careful about the maximum message size you could send over a WebRTC data channel. Especially if the data channel had been established between Firefox and Chrome. See here for a very good explanation of the problem.
The good news is that bug 979417, a big contribution by Lennart Grahl, has landed in Firefox 57, which adds EOR handling to Firefox data channels.