Complete "Play music with Simple Controls" functionality in Vaani which will be described in the Visual Design Specification and User Flows Specification of Bug 1172875

Assign this issue to myself since we may try to implement this through IAC at music app.

We already had the music playing control at system app's IAC media_conn. I will try to leverage it.

We had made an overall design to support both bug 1178273 and bug 1172881. Please see URL to have more information.

We would like to use one IAC connection handle both bug 1178273 and bug 1172881 to prevent too many IAC connections to system app. With the design mentioned by [1], we will use "music-controller" to open music player to play and to control music player. During playing, music player will send message back to notify Vaani the change of playing track and its metadata. That means the IAC port should be opened at Vaani to listen the changes. If a user kills the music app, the IAC port held by Vaani becomes useless. But Vaani doesn't have a way to know the remote is closed because of bug 915880. So, we don't have an event to remove music widget from Vaani's UI even if music app is closed by user properly. [1] https://wiki.mozilla.org/Firefox_OS/Vaani/Music

Firefox OS is not being worked on