[Devtools] Removed DataGrid's hasChildren getter/setter to use functions

third_party/WebKit/Source/devtools/front_end/timeline/TimelineTreeView.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 /**
  * @unrestricted
  */
 Timeline.TimelineTreeView = class extends UI.VBox {
   constructor() {
     super();
     this.element.classList.add('timeline-tree-view');
@@ skipping 404 matching lines @@
 Timeline.TimelineTreeView.TreeGridNode = class extends Timeline.TimelineTreeView.GridNode {
   /**
    * @param {!TimelineModel.TimelineProfileTree.Node} profileNode
    * @param {number} grandTotalTime
    * @param {number} maxSelfTime
    * @param {number} maxTotalTime
    * @param {!Timeline.TimelineTreeView} treeView
    */
   constructor(profileNode, grandTotalTime, maxSelfTime, maxTotalTime, treeView) {
     super(profileNode, grandTotalTime, maxSelfTime, maxTotalTime, treeView);
-    this.hasChildren = this._profileNode.children ? this._profileNode.children.size > 0 : false;
+    this.setHasChildren(this._profileNode.children ? this._profileNode.children.size > 0 : false);
     profileNode[Timeline.TimelineTreeView.TreeGridNode._gridNodeSymbol] = this;
   }
 
   /**
    * @override
    */
   populate() {
     if (this._populated)
       return;
     this._populated = true;
@@ skipping 502 matching lines @@
 
   _onSelectionChanged() {
     this.dispatchEventToListeners(Timeline.TimelineStackView.Events.SelectionChanged);
   }
 };
 
 /** @enum {symbol} */
 Timeline.TimelineStackView.Events = {
   SelectionChanged: Symbol('SelectionChanged')
 };