Bug 1016277 - If two different apps try to use the 'telephony' channel at the same time both apps can play audio.

See bug https://bugzilla.mozilla.org/show_bug.cgi?id=1016277 please.

These are the Loop app bits we need to add if we want the Loop app to compete correctly for the telephony audio channel.
Could we call it `addListener` instead? This let us to avoid errors between this method and the regular `addEventListener`