// Execute the runnable immediately. Because of scheduling this may end up getting called before
    // some of the previously added runnables, but we're OK with that. If we want to change the
    // contract to guarantee ordering among runnables we'd have to modify the logic here to allow
    // it.
    executeListener(runnable, executor);
  }

  /**
   * Runs this execution list, executing all existing pairs in the order they were added. However,