Firefox 34 released

Considering the video/audio chat is done with HTML5 and WebRTC... something Firefox already supported... and most of the work is done in Javascript I think... and the tiny bits they added to allow it to generate a URL... I don't think adding the chat feature really did much to bloat it. Given that the vast majority of chat services require an account and don't offer much in the way of privacy and security (so far as I'm concerned) actually offering encrypted P2P chat without the need for (much of) a third-party is a big thing. For many it will probably eliminate the desire for something like Skype.

Anyway, to answer your question... you can probably compile it from source without that... or use any of the other browsers that have a "we want to be smaller" goal. I'm not really familiar with any of that so I'll leave that as an exercise for the reader.