DevTools: Speed up timeline aggregated tree building.

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

 // Copyright 2017 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.EventsTimelineTreeView = class extends Timeline.TimelineTreeView {
   /**
    * @param {!TimelineModel.TimelineModel} model
@@ skipping 38 matching lines @@
     this.refreshTree();
     if (selectedEvent)
       this._selectEvent(selectedEvent, false);
   }
 
   /**
    * @param {!SDK.TracingModel.Event} event
    * @return {?TimelineModel.TimelineProfileTree.Node}
    */
   _findNodeWithEvent(event) {
-    var iterators = [this._currentTree.children.values()];
+    var iterators = [this._currentTree.children().values()];
 
     while (iterators.length) {
       var iterator = iterators.peekLast().next();
       if (iterator.done) {
         iterators.pop();
         continue;
       }
       var child = /** @type {!TimelineModel.TimelineProfileTree.Node} */ (iterator.value);
       if (child.event === event)
         return child;
-      if (child.children)
-        iterators.push(child.children.values());
+      iterators.push(child.children().values());
     }
     return null;
   }
 
   /**
    * @param {!SDK.TracingModel.Event} event
    * @param {boolean=} expand
    */
   _selectEvent(event, expand) {
     var node = this._findNodeWithEvent(event);
@@ skipping 170 matching lines @@
     this.dispatchEventToListeners(Timeline.EventsTimelineTreeView.Filters.Events.FilterChanged);
   }
 };
 
 Timeline.EventsTimelineTreeView.Filters._durationFilterPresetsMs = [0, 1, 15];
 
 /** @enum {symbol} */
 Timeline.EventsTimelineTreeView.Filters.Events = {
   FilterChanged: Symbol('FilterChanged')
 };