Add a timeline view to about:net-internals.

chrome/test/data/webui/net_internals/main.js

 // Copyright (c) 2011 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.
 
 /**
  * Checks visibility of tab handles against expectations, and navigates to all
  * tabs with visible handles, validating visibility of all other tabs as it
  * goes.
  */
 netInternalsTest.test('netInternalsTourTabs', function() {
   // Prevent sending any events to the browser as we flip through tabs, since
   // this tests is just intended to make sure everything's created and hooked
   // up properly Javascript side.
   g_browser.disable();
 
   // Expected visibility state of each tab.
   var tabVisibilityState = {
     capture: true,
     export: true,
     import: true,
     proxy: true,
     events: true,
+    timeline: true,
     dns: true,
     sockets: true,
     spdy: true,
     httpCache: true,
     httpThrottling: true,
     serviceProviders: cr.isWindows,
     tests: true,
     hsts: true,
     logs: cr.isChromeOS,
     prerender: true
   };
 
   netInternalsTest.checkTabHandleVisibility(tabVisibilityState, true);
 
   testDone();
 });