title: GWT treemap add mouseover/mouseout events
body: <p>I have written a google visualization treemap wrapper for GWT.
  I can successfully draw a treemap using it.
  But i am stuck with mouse events.
   How can i add mouseover/mouseout event to it? </p>
  
  <pre><code>public class TreeMap extends Visualization&lt;TreeMap.Options&gt;
  {
   public static class Options extends AbstractDrawOptions {
     public static Options create() {
         return JavaScriptObject.createObject().cast();
     }
  
     protected Options() {
     }
  
  
  
  
   }
  
   public static final String PACKAGE = "treemap";
  
   public TreeMap() {
     super();
   }
  
   public TreeMap(AbstractDataTable data, Options options) {
     super(data, options);
   }
  
   @Override
   protected native JavaScriptObject createJso(Element parent) /*-{
     return new $wnd.google.visualization.TreeMap(parent);
  
   }-*/;
   }
  </code></pre>