tools/perf/page_sets/deterministic_performance_counters.js

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // Monkey patch performance to get deterministic results.
   6 (function () {
   7   // Web page replay patches Data.now().
   8   var start_time = Date.now();
   9   var now_counter = 0;
  10   function now() {
  11      return now_counter++;
  12   }
  13   function timing() {
  14     // These values are arbitrary.
  15     // They are obtained by sampling "performance.now()" on a live web site.
  16     return {
  17       "navigationStart": start_time,
  18       "unloadEventStart": 0,
  19       "unloadEventEnd": 0,
  20       "redirectStart": 0,
  21       "redirectEnd": 0,
  22       "fetchStart": start_time + 94,
  23       "domainLookupStart": start_time + 94,
  24       "domainLookupEnd": start_time + 94,
  25       "connectStart": start_time + 94,
  26       "connectEnd": start_time + 94,
  27       "secureConnectionStart":0,
  28       "requestStart": start_time + 98,
  29       "responseStart": start_time + 546,
  30       "responseEnd": start_time + 1511,
  31       "domLoading": start_time + 562,
  32       "domInteractive": start_time + 1647,
  33       "domContentLoadedEventStart": start_time + 1647,
  34       "domContentLoadedEventEnd": start_time + 1654,
  35       "domComplete": start_time + 2009,
  36       "loadEventStart": start_time + 2009,
  37       "loadEventEnd": start_time + 2009
  38     };
  39   }
  40   Object.defineProperty(window, "performance", {
  41     get : function() {
  42             return { 'now' : now, 'timing' : timing() };
  43           }
  44   });
  45 })();