code: protected void addNavigationBarHeader(Content body) {
          Content htmlTree = (configuration.allowTag(HtmlTag.HEADER))
                  ? HtmlTree.HEADER()
                  : body;
          addTop(htmlTree);
          addNavLinks(true, htmlTree);
          if (configuration.allowTag(HtmlTag.HEADER)) {
              body.addContent(htmlTree);
          }
      }
docs: Adds the top text (from the -top option), the upper
  navigation bar, and then the title (from the"-title"
  option), at the top of page.
  
  @param body the documentation tree to which the navigation bar header will be added