As it's a tarako only patch, I still try to make it not so workaround and possible to extend if we want this become a new feature in the future, so I followed how we named the functions in the media playback widget in system, like `openMediaApp` (https://github.com/mozilla-b2g/gaia/blob/master/apps/system/js/media_playback.js#L120), though I made the music origin as a constant, but if we also send the origin (https://github.com/mozilla-b2g/gaia/blob/master/apps/system/js/media_playback.js#L74) from the media playback widget to the media app agent instead of using the constant music origin, that should make more sense I believe, so I will do that then keep `_tellMediaAppToResume` and `_launchMediaApp` as they are.