Fix WebBluetooth generator to distinguish between different methods.

third_party/WebKit/LayoutTests/bluetooth/script-tests/gatt-op-device-disconnects-during-error.js

-'use strict';
-promise_test(() => {
-  let val = new Uint8Array([1]);
-  return setBluetoothFakeAdapter('FailingGATTOperationsAdapter')
-    .then(() => requestDeviceWithKeyDown({
-      filters: [{services: [errorUUID(0xA0)]}],
-      optionalServices: [request_disconnection_service_uuid]
-    }))
-    .then(device => device.gatt.connect())
-    .then(gattServer => {
-      let error_characteristic;
-      return gattServer
-        .getPrimaryService(errorUUID(0xA0))
-        .then(es => es.getCharacteristic(errorUUID(0xA1)))
-        .then(ec => error_characteristic = ec)
-        .then(() => get_request_disconnection(gattServer))
-        .then(requestDisconnection => {
-          requestDisconnection();
-          return assert_promise_rejects_with_message(
-            error_characteristic.CALLS([
-              readValue()|
-              writeValue(val)|
-              startNotifications()]),
-            new DOMException(
-              'GATT Server disconnected while performing a GATT operation.',
-              'NetworkError'));
-        });
-    });
-}, 'Device disconnects during a FUNCTION_NAME call that fails. ' +
-   'Reject with NetworkError.');