Fix WebBluetooth generator to distinguish between different methods.

third_party/WebKit/LayoutTests/bluetooth/script-tests/service/device-disconnects-invalidates-objects.js

 'use strict';
 promise_test(() => {
   return setBluetoothFakeAdapter('DisconnectingHealthThermometerAdapter')
     .then(() => requestDeviceWithKeyDown({
       filters: [{services: ['health_thermometer']}],
       optionalServices: [request_disconnection_service_uuid]}))
     .then(device => device.gatt.connect())
     .then(gattServer => {
       let characteristics;
       return gattServer.getPrimaryService('health_thermometer')
@@ skipping 31 matching lines @@
             error));
         promises = promises.then(() =>
           assert_promise_rejects_with_message(
             characteristic.stopNotifications(),
             error));
       }
       return promises;
     });
 }, 'Calls on characteristics after device disconnects and we reconnect. ' +
    'Should reject with InvalidStateError.');