code: public void addSrcLink(Element typeElement, Content label, Content htmltree) {
          if (typeElement == null) {
              return;
          }
          TypeElement te = utils.getEnclosingTypeElement(typeElement);
          if (te == null) {
              // must be a typeElement since in has no containing class.
              te = (TypeElement) typeElement;
          }
          DocPath href = pathToRoot
                  .resolve(DocPaths.SOURCE_OUTPUT)
                  .resolve(DocPath.forClass(utils, te));
          Content linkContent = getHyperLink(href
                  .fragment(SourceToHTMLConverter.getAnchorName(utils, typeElement)), label, "", "");
          htmltree.addContent(linkContent);
      }
docs: Add the link to the content tree.
  
  @param typeElement program element typeElement for which the link will be added
  @param label label for the link
  @param htmltree the content tree to which the link will be added