...and change this to be:

`      <spark-overlay id="overlay" class="slideup"
          opened="{{opened}}" modal autoCloseDisabled on-activate={{toggle}}>
`
Note the `on-activate...` part that I've added: it will intercept the event bubbling up from the underlying `overlay` and close the menu. The even will keep propagating up, though, so the main client, which is `SparkPolymerMenu.onMenuSelected()`, will still receive it and act accordingly.