code: function TreeOutline(listNode)
  {
      this.children = [];
      this.selectedTreeElement = null;
      this._childrenListNode = listNode;
      this._childrenListNode.removeChildren();
      this._knownTreeElements = [];
      this._treeElementsExpandedState = [];
      this.expandTreeElementsWhenArrowing = false;
      this.root = true;
      this.hasChildren = false;
      this.expanded = true;
      this.selected = false;
      this.treeOutline = this;
  
      this._childrenListNode.tabIndex = 0;
      this._childrenListNode.addEventListener("keydown", this._treeKeyDown.bind(this), true);
  }
docs: /*
  Copyright (C) 2007 Apple Inc.  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions
  are met:
  
  1.  Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.
  2.  Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.
  3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  its contributors may be used to endorse or promote products derived
  from this software without specific prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.