Bug 1041987 - [Tarako] Music audio rings for 2~3s when kill music in car...

...d view after music in-process
The 200ms looks tricky to me, but I believe you have tested it and it works. Though it's a workaround but let's try to make it robust. I think there are two possible ways to make sure music app does stop.

The first way is to wait the playback status changed to STOP in the MediaPlaybackWidget, after we send the STOP command, we can assume the MediaPlaybackWidget receive the STOP status as well, but this probably needs more code to implement it, so might not be a quick choice for us.

The second way is to listen to the 'audio-channel-changed' mozChromeEvent, like what we did in the sound manager in system app. This is probably more reliable than the other approaches because the event means the content channel(which music app used) is no longer the active channel, and it should be a good time to kill the music app because we are sure the playback status is STOP.

If we don't have more time to fix this then I am fine with the current patch.