I am not able to make a contentpanel resize when the browser is resized. The below code renders the content panel to fill the screen(desired) but doesnt resize when the browser window size is changed.

Code:
 public void onModuleLoad() {
     RootPanel rootPanel = RootPanel.get();
     Viewport viewPort = new Viewport();
     final Layout layout = new FitLayout();
     ContentPanel resultPanel = new ContentPanel();
     resultPanel.setHeading("Result");
     resultPanel.setFrame(true);
     resultPanel.setLayout(layout);
     resultPanel.setScrollMode(Scroll.ALWAYS);
     resultPanel.addButton(new Button("OK"));
     resultPanel.setWidth("100%");
     LayoutContainer page = new LayoutContainer(new RowLayout(Orientation.VERTICAL));
     page.add(resultPanel, new com.extjs.gxt.ui.client.widget.layout.RowData(1, -1));
     viewPort.add(page);


     rootPanel.add(viewPort);
     page.layout();


 }