Last modified: 2014-02-04 11:32:45 UTC
It seems to disable a few specific mobile browsers (??) and old versions of Opera. Should find out what actually breaks and try to detect on that -- for instance if it breaks on "iphone" it presumably breaks on an ipad too... or what if it's been fixed?
Having just had to add another $.client test there (bug 50805), I hereby decree this is most likely not possible.