code: private void addAllClassesFrameTag(Content contentTree) {
          HtmlTree frame = HtmlTree.IFRAME(DocPaths.ALLCLASSES_FRAME.getPath(),
                  "packageFrame", configuration.getText("doclet.All_classes_and_interfaces"));
          HtmlTree leftBottom = HtmlTree.DIV(HtmlStyle.leftBottom, frame);
          contentTree.addContent(leftBottom);
      }
docs: Add the IFRAME tag for the frame that lists all classes.
  
  @param contentTree the content tree to which the information will be added