code: protected void addOverviewHeader(Content body) {
          if (root.inlineTags().length > 0) {
              HtmlTree subTitleDiv = new HtmlTree(HtmlTag.DIV);
              subTitleDiv.addStyle(HtmlStyle.subTitle);
              addSummaryComment(root, subTitleDiv);
              Content div = HtmlTree.DIV(HtmlStyle.header, subTitleDiv);
              Content see = seeLabel;
              see.addContent(" ");
              Content descPara = HtmlTree.P(see);
              Content descLink = getHyperLink(getDocLink(
                      SectionName.OVERVIEW_DESCRIPTION),
                      descriptionLabel, "", "");
              descPara.addContent(descLink);
              div.addContent(descPara);
              body.addContent(div);
          }
      }
docs: Adds the overview summary comment for this documentation. Add one line
  summary at the top of the page and generate a link to the description,
  which is added at the end of this page.
  
  @param body the documentation tree to which the overview header will be added