code: function ListView_createAriaMarkers() {
                      if (!this._viewport.getAttribute("aria-label")) {
                          this._viewport.setAttribute("aria-label", strings.listViewViewportAriaLabel);
                      }
  
                      if (!this._ariaStartMarker) {
                          this._ariaStartMarker = _Global.document.createElement("div");
                          this._ariaStartMarker.id = uniqueID(this._ariaStartMarker);
                          this._viewport.insertBefore(this._ariaStartMarker, this._viewport.firstElementChild);
                      }
                      if (!this._ariaEndMarker) {
                          this._ariaEndMarker = _Global.document.createElement("div");
                          this._ariaEndMarker.id = uniqueID(this._ariaEndMarker);
                          this._viewport.appendChild(this._ariaEndMarker);
                      }
                  }
docs: If they don't yet exist, create the start and end markers which are required by Narrator's aria-flowto/flowfrom implementation. They mark the start and end of ListView's set of out-of-order DOM elements and so they must surround the headers and groups in the DOM.