hook up audio tests

[fippo]

@Pehrsons has some nice webaudio tests for mozilla:
http://searchfox.org/mozilla-central/rev/2142de26c16c05f23e543be4fa1a651c4d29604e/dom/media/tests/mochitest/head.js#33
http://searchfox.org/mozilla-central/rev/2142de26c16c05f23e543be4fa1a651c4d29604e/dom/media/tests/mochitest/test_getUserMedia_addTrackRemoveTrack.html#119