code: public void setContentHighlightingVisible(boolean visible) {
  
          if (visible) {
              if (m_highlighting == null) {
                  m_highlighting = new CmsHighlightingBorder(
                      CmsPositionBean.getBoundingClientRect(m_referenceElement),
                      CmsHighlightingBorder.BorderColor.red);
                  RootPanel.get().add(m_highlighting);
              } else {
                  m_highlighting.setPosition(CmsPositionBean.getBoundingClientRect(m_referenceElement));
              }
          } else {
              if (m_highlighting != null) {
                  m_highlighting.removeFromParent();
                  m_highlighting = null;
              }
          }
      }
docs: Sets the visibility of the reference element highlighting border.<p>
  
  @param visible <code>true</code> to show the highlighting