DevTools: Fix "Entries disappear after selecting 'Group by Domain' option in 'Performance' Bottom-U…

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 845 matching lines @@
     var domainMatch = /([^.]*\.)?[^.]*$/.exec(parsedURL.host);
     return domainMatch && domainMatch[0] || '';
   }
 
   /**
    * @param {!SDK.TracingModel.Event} event
    * @return {string}
    */
   _productByEvent(event) {
     var url = TimelineModel.TimelineProfileTree.eventURL(event);
-    if (!url)
+    if (!url || !this._productByURLCache)
       return '';
     if (this._productByURLCache.has(url))
       return this._productByURLCache.get(url);
     if (!this._productRegistry)
       return '';
     var parsedURL = url.asParsedURL();
     var name = parsedURL && this._productRegistry.nameForUrl(parsedURL) || '';
     this._productByURLCache.set(url, name);
     return name;
   }
@@ skipping 140 matching lines @@
 
   _onSelectionChanged() {
     this.dispatchEventToListeners(Timeline.TimelineStackView.Events.SelectionChanged);
   }
 };
 
 /** @enum {symbol} */
 Timeline.TimelineStackView.Events = {
   SelectionChanged: Symbol('SelectionChanged')
 };