message: refactor(AsyncAction): add return statement to make stricter TS builds happy
  This is an issue encountered in google3, which builds under stricter rules than we do, Google has been modifying this file locally to get around that (we build from the TS sources), this is just upstreaming that modification.
diff: @@ -80,6 +80,7 @@ export class AsyncAction<T> extends Action<T> {
  // Otherwise, if the action's delay time is different from the current delay,
  // or the action has been rescheduled before it's executed, clear the interval id
  clearInterval(id);
  + return undefined;
  }
  /**
  