Changes

'''BluetoothAdapterEventBluetoothAdapterAddedEvent''' is carried as the argument of [https://wiki.mozilla.org/B2G/Bluetooth/WebBluetooth-v2/BluetoothManager#onadapteradded manager.onadapteradded] event handler. Applications can get the added [https://wiki.mozilla.org/B2G/Bluetooth/WebBluetooth-v2/BluetoothAdapter BluetoothAdapter] object and knows whether the added adapter is default adapter.