      /**
       * The constants used in this Content Widget.
       */
      public static interface CwConstants extends Constants,
          ContentWidget.CwConstants {
        String cwFrameDescription();

        String cwFrameName();

        String cwFrameSetLocation();
      }

      /**
       * An instance of the constants.
       */
      private CwConstants constants;

      /**
       * Initialize this example.
       */
      @Override
      public Widget onInitialize() {
        // Create a new frame
        String url = GWT.getModuleBaseURL();
        final Frame frame = new Frame(url);
        frame.setSize("700px", "300px");
        frame.ensureDebugId("cwFrame");

        // Create a form to set the location of the frame
        final TextBox locationBox = new TextBox();
        locationBox.setText(url);
        Button setLocationButton = new Button(constants.cwFrameSetLocation());
        HorizontalPanel optionsPanel = new HorizontalPanel();
        optionsPanel.setSpacing(8);
        optionsPanel.add(locationBox);
        optionsPanel.add(setLocationButton);

        // Change the location when the user clicks the button
        setLocationButton.addClickListener(new ClickListener() {
          public void onClick(Widget sender) {
            frame.setUrl(locationBox.getText());
          }
        });

        // Change the location when the user presses enter
        locationBox.addKeyboardListener(new KeyboardListenerAdapter() {
          @Override
          public void onKeyPress(Widget sender, char keyCode, int modifiers) {
            if (keyCode == KEY_ENTER) {
              frame.setUrl(locationBox.getText());
            }
          }
        });

        // Add everything to a panel and return it
        VerticalPanel vPanel = new VerticalPanel();
        vPanel.add(optionsPanel);
        vPanel.add(frame);
        return vPanel;
      }