Changes

: The method makes the device's adapter start seeking for remote devices. The discovery process may be terminated after discovering a period of time. If the startDiscovery operation succeeds, an [[B2G/Bluetooth/WebBluetooth-v2/BluetoothAdapter#onattributechanged|onattributechanged]] event would be triggered before the Promise is resolved to indicate property [[B2G/Bluetooth/WebBluetooth-v2/BluetoothAdapter#discovering|adapter.discovering]] becomes true.