rem: return null; 
add: return this.tree; 
context:   getBestItem: function ()  {    var seln = this.getSelection ();    if (seln.length < 1) {      var kids = ContentUtils.childByLocalName(this.tree, "treechildren");      if (kids) return kids.lastChild;    }    else      return seln[0];    return null;  },
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/b58a221f2fde203195889c6df948140558b290e2/bookmarksTree.js/clean/xpfe/components/bookmarks/resources/bookmarksTree.js