DevTools: Speed up timeline aggregated tree building.

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

Index: third_party/WebKit/Source/devtools/front_end/timeline/EventsTimelineTreeView.js
diff --git a/third_party/WebKit/Source/devtools/front_end/timeline/EventsTimelineTreeView.js b/third_party/WebKit/Source/devtools/front_end/timeline/EventsTimelineTreeView.js
index 6df91d2427395b1b83babe8ef8f4000c3a9c6087..baa94a984d741aedf4920257f340987939856de5 100644
--- a/third_party/WebKit/Source/devtools/front_end/timeline/EventsTimelineTreeView.js
+++ b/third_party/WebKit/Source/devtools/front_end/timeline/EventsTimelineTreeView.js
@@ -56,7 +56,7 @@ Timeline.EventsTimelineTreeView = class extends Timeline.TimelineTreeView {
    * @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();
@@ -67,8 +67,7 @@ Timeline.EventsTimelineTreeView = class extends Timeline.TimelineTreeView {
       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;
   }