mozilla-b2g/gaia — pull request #9249 by gtorodelvalle (2013-04-17 17:42:24+00:00)
Title: Dialer bug 857951 busy tone from etiennesegonzac bug 859354 call waiting alert

Playing the busy tone in case the calling party is occupied. Basically, we play a 3 seconds long busy tone letting the user stop it clicking on the call hang up button.