Fix startup_metric racing condition: It used to wait t.WaitForDocumentReadyStateToBeComplete() befo…

tools/perf/metrics/startup_metric.py

 # Copyright 2013 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.
 import collections
 import json
 import logging
 
 from metrics import Metric
 
 from telemetry.core import exceptions
@@ skipping 29 matching lines @@
         tab)
     if high_bytes == 0 and low_bytes == 0:
       return None
     return (int(high_bytes) << 32) | (int(low_bytes) << 1)
 
   def _RecordTabLoadTimes(self, tab, browser_main_entry_time_ms, results):
     """Records the tab load times for the browser. """
     tab_load_times = []
     TabLoadTime = collections.namedtuple(
         'TabLoadTime',
-        ['load_start_ms', 'load_duration_ms', 'request_start_ms'])
+        ['request_start_ms', 'load_end_ms'])

[nednguyen, 2015/03/30 21:25:41]

What is this renaming about?

[cylee1, 2015/03/31 10:52:27]

load_start_ms + load_duration_ms = load_end_ms
it's just window.performance.timing gives load_end_ms directly, so we don't need
to sum them up manually.

 
     def RecordTabLoadTime(t):
       try:
-        t.WaitForDocumentReadyStateToBeComplete()
-
-        result = t.EvaluateJavaScript(
-            'statsCollectionController.tabLoadTiming()')
-        result = json.loads(result)
-

[nednguyen, 2015/03/30 21:25:41]

What are these change about?

[cylee1, 2015/03/31 10:52:27]

Explained in mail.

-        if 'load_start_ms' not in result or 'load_duration_ms' not in result:
-          raise Exception("Outdated Chrome version, "
-              "statsCollectionController.tabLoadTiming() not present")
-        if result['load_duration_ms'] is None:
-          tab_title = t.EvaluateJavaScript('document.title')
-          print "Page: ", tab_title, " didn't finish loading."
-          return
+        t.WaitForJavaScriptExpression(
+            'window.performance.timing["loadEventEnd"] > 0', 10)
 
         perf_timing = t.EvaluateJavaScript('window.performance.timing')
         if 'requestStart' not in perf_timing:
           perf_timing['requestStart'] = 0  # Exclude from benchmark results
           print 'requestStart is not supported by this browser'
 
         tab_load_times.append(TabLoadTime(
-            int(result['load_start_ms']),
-            int(result['load_duration_ms']),
-            int(perf_timing['requestStart'])))
+            int(perf_timing['requestStart']),
+            int(perf_timing['loadEventEnd'])))
       except exceptions.TimeoutException:
         # Low memory Android devices may not be able to load more than
         # one tab at a time, so may timeout when the test attempts to
         # access a background tab. Ignore these tabs.
         logging.error("Tab timed out on JavaScript access")
 
     # Only measure the foreground tab. We can't measure all tabs on Android
     # because on Android the data of the background tabs is loaded on demand,
     # when the user switches to them, rather than during startup. In view of
     # this, to get the same measures on all platform, we only measure the
     # foreground tab on all platforms.
 
     RecordTabLoadTime(tab.browser.foreground_tab)
 
     foreground_tab_stats = tab_load_times[0]
-    foreground_tab_load_complete = ((foreground_tab_stats.load_start_ms +
-        foreground_tab_stats.load_duration_ms) - browser_main_entry_time_ms)
+    foreground_tab_load_complete = (
+        foreground_tab_stats.load_end_ms - browser_main_entry_time_ms)
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'foreground_tab_load_complete', 'ms',
         foreground_tab_load_complete))
     if (foreground_tab_stats.request_start_ms > 0):
       results.AddValue(scalar.ScalarValue(
           results.current_page, 'foreground_tab_request_start', 'ms',
           foreground_tab_stats.request_start_ms - browser_main_entry_time_ms))
 
   def AddResults(self, tab, results):
     get_histogram_js = 'statsCollectionController.getBrowserHistogram("%s")'
@@ skipping 13 matching lines @@
 
       results.AddValue(scalar.ScalarValue(
           results.current_page, display_name, 'ms', measured_time))
 
     # Get tab load times.
     browser_main_entry_time_ms = self._GetBrowserMainEntryTime(tab)
     if (browser_main_entry_time_ms is None):
       print "Outdated Chrome version, browser main entry time not supported."
       return
     self._RecordTabLoadTimes(tab, browser_main_entry_time_ms, results)