function compareStartTime(a, b)
        {
            var nodeA = /** @type {!WebInspector.TimelineTreeView.GridNode} */ (a);
            var nodeB = /** @type {!WebInspector.TimelineTreeView.GridNode} */ (b);
            return nodeA._profileNode.event.startTime - nodeB._profileNode.event.startTime;
        }
@param {!WebInspector.DataGridNode} a
@param {!WebInspector.DataGridNode} b
@return {number}