I used the following code snippet and I cannot get rid of the unwanted margin on the left and top of the viewport

Code:
public class MySampleApplication implements EntryPoint, IsWidget  {

    public void onModuleLoad() {
        Viewport viewport = new Viewport();
        viewport.setWidget(this);
        RootPanel.get().add(viewport);
    }


    public Widget asWidget() {


           final BorderLayoutContainer con = new BorderLayoutContainer();
           con.setBorders(true);
           con.setLayoutData(new MarginData(0, 0, 0, 0));


           return con;
       }
}
it shows up as (tried it in chrome and ie9) :
marginissue.jpg
Am I overlooking something here?