Fix WebBluetooth generator to distinguish between different methods.

third_party/WebKit/LayoutTests/bluetooth/script-tests/gatt-op-disconnect-called-before.js

-'use strict';
-promise_test(() => {
-  let val = new Uint8Array([1]);
-  return setBluetoothFakeAdapter('DisconnectingHealthThermometerAdapter')
-    .then(() => requestDeviceWithKeyDown({
-      filters: [{services: ['health_thermometer']}]}))
-    .then(device => device.gatt.connect())
-    .then(gattServer => {
-      return gattServer.getPrimaryService('health_thermometer')
-        .then(service => service.getCharacteristic('measurement_interval'))
-        .then(measurement_interval => {
-          gattServer.disconnect();
-          return assert_promise_rejects_with_message(
-            measurement_interval.CALLS([
-              readValue()|
-              writeValue(val)|
-              startNotifications()|
-              stopNotifications()]),
-            new DOMException(
-              'GATT Server is disconnected. Cannot perform GATT operations.',
-              'NetworkError'));
-        });
-    });
-}, 'disconnect() called before FUNCTION_NAME. Reject with NetworkError.');