Fix WebBluetooth generator to distinguish between different methods.

third_party/WebKit/LayoutTests/bluetooth/script-tests/server/get-different-service-after-reconnection.js

 'use strict';
 promise_test(() => {
   return setBluetoothFakeAdapter('TwoHeartRateServicesAdapter')
     .then(() => requestDeviceWithKeyDown({
       filters: [{services: ['heart_rate']}],
       optionalServices: ['generic_access']}))
     .then(device => device.gatt.connect())
     .then(gattServer => {
       let services1;
       return gattServer
@@ skipping 17 matching lines @@
         assert_equals(services_arrays[0].length, services_arrays[i].length);
       }
 
       let base_set = new Set(services_arrays.shift());
       for (let services of services_arrays) {
         services.forEach(service => assert_false(base_set.has(service)));
       }
     });
 }, 'Calls to FUNCTION_NAME after a disconnection should return a ' +
    'different object.');