static/ext/src/data/TreeStore.js
function(node1, node2) {
        return node1[node1.persistenceProperty].index - node2[node2.persistenceProperty].index;
    }
function(node1, node2) {
        return node1[node1.persistenceProperty].index - node2[node2.persistenceProperty].index;
    }
Sorter function for sorting records in index order
@private
@param {Ext.data.NodeInterface} node1
@param {Ext.data.NodeInterface} node2
@return {Number}