I installed the GMail app onto my Ubuntu 15.04 machine.

Upon logging in, a warning message appears, saying `This version of Safari is no longer supported. Please upgrade to a supported browser`

I then received an email from Google saying that my GMail account had been accessed from Safari running on an unknown OS. 

Safari? Unknown OS? What's the reason for this? 

I'm presuming that it's an issue with the user agent data set by browsers is missing or incorrect in the GMail app, which leads me to my second question - the Ubuntu "apps" are clearly just slimmed down web browsers, but which browser are they based on?