We fire a notification in system::bluetooth_transfer.js while file is sending.
According to UX spec., it will need to fire another notification to figure out the state.  So, we need the permission.(Spec. Version 0.2, p10, figure6)

I think it's a little bit redundant message in this case, since we have a progress of transferring task on utility tray. But UX concern to have the notification immediately.