Iceweasel is my primary web browser in Debian Jessie and I use it for Google Hangouts too. Recently a month back one fine day when I was about to start with a meeting after an 'apt-get upgrade' on my Debian machine, Google Hangouts stopped working in Iceweasel. Google marked Iceweasel as an unsupported browser and I was left without an option. Enormous searching asked me to use a different user-agent string to act as a supported browser, which also failed in my case. Even with a changed user-agent string Google rejected my Hangout sessions. I haven't been so very comfortable with Google Chrome web browser (experienced from past usages) and didn't want to try it on my Debian Jessie machines, just for Google Hangouts.
Another option I was left with is to install Firefox web browser which is in the supported list of web browsers for Google Hangouts. But the problem with installing Firefox on Debian Jessie is, there isn't a Debian package or an apt repository provided by Mozilla :( I did experienced installing Firefox from source in the past, but that is a maintainance headache when it comes to updates and also managing the paths. These days I ve become very lazy - I am looking for Debian packages for installation rather than installing from source, except for projects that I develop ;) With no options left though, I was using the Firefox installed from source in my Debian Jessie box.
Yesterday, I saw some light in the tunnel to have a Debianistic way to solve this problem. I met with "Iceweasel Aurora" which is the bleeding edge release of Firefox that is ready to get into Debian Experimental (I do not care on experimental tag on Debian, since people run full-fledged GNU/Linux server OS based on Debian sid :D ). Interestingly Iceweasel Aurora didn't had any problems with starting a Google Hangout session, partly due to the following user-agent string found in Aurora release.
Once the above line is added, use the following commands to install Iceweasel Aurora release.
And that made Google Hangouts work for me again.
RANT: Since Iceweasel is same as Firefox, Google should think about adding Iceweasel to its permanently supported browsers list!