I see no reason why things shouldn't 'just
work'. And I've been
wondering: is this a long-standing problem with ALSA's Jack
plugin, or are the browsers doing something wrong ?
As far as I know the ALSA Jack plugin has issues:
http://jackaudio.org/faq/routing_alsa.html#using-the-alsa-jack-pcm-plugin
It also introduces some extra latency because of an extra buffer, maybe
you're running into issues there?
Jeremy