docs: protected static Button getFlushToolButton() {
  
          Button res = new Button(FontOpenCms.CACHE);
          res.addStyleName(ValoTheme.BUTTON_BORDERLESS);
          res.addStyleName(OpenCmsTheme.TOOLBAR_BUTTON);
          res.addClickListener(new ClickListener() {
  
              /**vaadin serial id. */
              private static final long serialVersionUID = 7110311791006484514L;
  
              public void buttonClick(ClickEvent event) {
  
                  Window window = CmsBasicDialog.prepareWindow(DialogWidth.content);
  
                  window.setContent(new CmsFlushButtonHolderDialog(window));
                  A_CmsUI.get().addWindow(window);
              }
  
          });
          return res;
      }