title: Add handler to list box for when user opens list box?
body: <p>How do I add a handler to when a user just clicks on a list box but doesn't actually select anything?  As far as I can tell, onclick on fires when the user selects an item in the dropdown and not when they actually click on it to see the options.</p>
  
  <p>(Bonus points if you know how to do this in GWT instead of just raw javascript).</p>
  
  <p>Thanks!</p>