code: @SuppressWarnings("serial")
      private Component createCloseButton() {
  
          Button closeBtn = CmsToolBar.createButton(
              FontOpenCms.CIRCLE_INV_CANCEL,
              m_messages.key(Messages.GUI_BUTTON_CANCEL_0));
          closeBtn.addClickListener(new ClickListener() {
  
              public void buttonClick(ClickEvent event) {
  
                  closeAction();
              }
  
          });
          return closeBtn;
      }
docs: Create the close button UI Component.
  @return the close button.