code: function PDFOutlineViewer_toggleOutlineItem(root, show) {
              this.lastToggleIsShow = show;
              var togglers = root.querySelectorAll('.outlineItemToggler');
              for (var i = 0, ii = togglers.length; i < ii; ++i) {
                togglers[i].classList[show ? 'remove' : 'add']('outlineItemsHidden');
              }
            }
docs: Toggle the visibility of the subtree of an outline item.
  
  @param {Element} root - the root of the outline (sub)tree.
  @param {boolean} show - whether to show the outline (sub)tree. If false,
  the outline subtree rooted at |root| will be collapsed.
  
  @private