DevTools: update group-by combobox upon tree view change in timeline aggregated details.

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
  * @implements {UI.Searchable}
  */
 Timeline.TimelineTreeView = class extends UI.VBox {
   constructor() {
@@ skipping 613 matching lines @@
  * @unrestricted
  */
 Timeline.AggregatedTimelineTreeView = class extends Timeline.TimelineTreeView {
   /**
    * @param {!Array<!TimelineModel.TimelineModelFilter>} filters
    */
   constructor(filters) {
     super();
     this._groupBySetting =
         Common.settings.createSetting('timelineTreeGroupBy', Timeline.AggregatedTimelineTreeView.GroupBy.None);
+    this._groupByCombobox = new UI.ToolbarComboBox(this._onGroupByChanged.bind(this));
     this.init(filters);
     this._stackView = new Timeline.TimelineStackView(this);
     this._stackView.addEventListener(
         Timeline.TimelineStackView.Events.SelectionChanged, this._onStackViewSelectionChanged, this);
   }
 
   /**
    * @override
+   */
+  wasShown() {
+    var groupById = this._groupBySetting.get();
+    var option = this._groupByCombobox.options().find(option => option.value === groupById);
+    if (option)
+      this._groupByCombobox.select(option);
+  }
+
+  /**
+   * @override
    * @param {!Timeline.TimelineSelection} selection
    */
   updateContents(selection) {
     this._updateExtensionResolver();
     super.updateContents(selection);
     var rootNode = this._dataGrid.rootNode();
     if (rootNode.children.length)
       rootNode.children[0].revealAndSelect();
   }
 
@@ skipping 53 matching lines @@
     }
     return {name: node.id || Common.UIString('unattributed'), color: color};
   }
 
   /**
    * @override
    * @param {!UI.Toolbar} toolbar
    */
   populateToolbar(toolbar) {
     super.populateToolbar(toolbar);
-    this._groupByCombobox = new UI.ToolbarComboBox(this._onGroupByChanged.bind(this));
     /**
      * @param {string} name
      * @param {string} id
      * @this {Timeline.TimelineTreeView}
      */
     function addGroupingOption(name, id) {
       var option = this._groupByCombobox.createOption(name, '', id);
       this._groupByCombobox.addOption(option);
       if (id === this._groupBySetting.get())
         this._groupByCombobox.select(option);
@@ skipping 259 matching lines @@
 
   _onSelectionChanged() {
     this.dispatchEventToListeners(Timeline.TimelineStackView.Events.SelectionChanged);
   }
 };
 
 /** @enum {symbol} */
 Timeline.TimelineStackView.Events = {
   SelectionChanged: Symbol('SelectionChanged')
 };