code: static String getDropDownButtonHtml(ExternalResource icon) {
  
          return "<div tabindex=\"0\" role=\"button\" class=\"v-button v-widget borderless v-button-borderless "
              + OpenCmsTheme.TOOLBAR_BUTTON
              + " v-button-"
              + OpenCmsTheme.TOOLBAR_BUTTON
              + "\"><span class=\"v-button-wrap\"><img class=\"v-icon\" src=\""
              + icon.getURL()
              + "\" /></span></div>";
      }
docs: Creates the button HTML for the given icon resource.<p>
  
  @param icon the icon
  
  @return the HTML