[Android] Don't wait for background tabs

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 metrics import histogram_util
 
@@ skipping 23 matching lines @@
         'Startup.BrowserMainEntryTimeAbsoluteHighWord',
         tab)
     low_bytes = histogram_util.GetHistogramSum(
         histogram_type,
         'Startup.BrowserMainEntryTimeAbsoluteLowWord',
         tab)
     if high_bytes == 0 and low_bytes == 0:
       return None
     return (int(high_bytes) << 32) | (int(low_bytes) << 1)
 
-  # pylint: disable=W0101
+# pylint: disable=W0101
   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', 'is_foreground_tab'])
-    num_open_tabs = len(tab.browser.tabs)
-    for i in xrange(num_open_tabs):
+
+    def RecordTabLoadTime(t):
       try:
-        t = tab.browser.tabs[i]
         t.WaitForDocumentReadyStateToBeComplete()
 
         result = t.EvaluateJavaScript(
             'statsCollectionController.tabLoadTiming()')
         result = json.loads(result)
 
         if 'load_start_ms' not in result or 'load_duration_ms' not in result:
           raise Exception("Outdated Chrome version, "
               "statsCollectionController.tabLoadTiming() not present")
-          return
         if result['load_duration_ms'] is None:
           tab_title = t.EvaluateJavaScript('document.title')
           print "Page: ", tab_title, " didn't finish loading."
-          continue
+          return
 
         is_foreground_tab = t.EvaluateJavaScript('!document.hidden')
         tab_load_times.append(TabLoadTime(
             int(result['load_start_ms']),
             int(result['load_duration_ms']),
             is_foreground_tab))
       except util.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 number: %d timed out on JavaScript access" % i)
-        continue
-
-    # Postprocess results
-    load_complete_times = (
-        [t.load_start_ms + t.load_duration_ms for t in tab_load_times])
-    load_complete_times.sort()
+        logging.error("Tab number: %d timed out on JavaScript access" % 0)
 
     if 'android' in tab.browser.browser_type:
-      # document.hidden is broken on Android - crbug.com/322544.
-      foreground_tab_stats = [tab_load_times[0]]
+      # On android the background tabs are loaded on demand, so wont have been
+      # loaded at this stage; only record the foreground tab. Also
+      # document.hidden is broken on Android - crbug.com/322544 so assume this
+      # is tab[0]

[jeremy, 2014/02/13 09:40:15]

Can you stick in a comment explaining in detail the Android behavior and that
we're doing the same thing on all platforms so we get the same measurement on
all of them.

+      RecordTabLoadTime(tab.browser.tabs[0])
+
+      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)
+      results.Add(
+          'foreground_tab_load_complete', 'ms', foreground_tab_load_complete)
     else:
+      num_open_tabs = len(tab.browser.tabs)
+      for i in xrange(num_open_tabs):
+        RecordTabLoadTime(tab.browser.tabs[i])
+      # Postprocess results
+      load_complete_times = (
+          [t.load_start_ms + t.load_duration_ms for t in tab_load_times])
+      load_complete_times.sort()
+
       foreground_tab_stats = (
           [t for t in tab_load_times if t.is_foreground_tab == True])
-    if (len(foreground_tab_stats) != 1):
-      raise Exception ("More than one foreground tab? ", foreground_tab_stats)
-    foreground_tab_stats = foreground_tab_stats[0]
+      if (len(foreground_tab_stats) != 1):
+        raise Exception ("More than one foreground tab? ", foreground_tab_stats)
+      foreground_tab_stats = foreground_tab_stats[0]
 
-    # Report load stats.
-    foreground_tab_load_complete = ((foreground_tab_stats.load_start_ms +
-        foreground_tab_stats.load_duration_ms) - browser_main_entry_time_ms)
+      # Report load stats.
+      foreground_tab_load_complete = ((foreground_tab_stats.load_start_ms +
+          foreground_tab_stats.load_duration_ms) - browser_main_entry_time_ms)
 
-    results.Add(
-        'foreground_tab_load_complete', 'ms', foreground_tab_load_complete)
+      results.Add(
+          'foreground_tab_load_complete', 'ms', foreground_tab_load_complete)
 
-    if num_open_tabs > 1:
-      last_tab_load_complete = (
-          load_complete_times[-1] - browser_main_entry_time_ms)
-      results.Add('last_tab_load_complete', 'ms', last_tab_load_complete)
+      if num_open_tabs > 1:
+        last_tab_load_complete = (
+            load_complete_times[-1] - browser_main_entry_time_ms)
+        results.Add('last_tab_load_complete', 'ms', last_tab_load_complete)
 
   def AddResults(self, tab, results):
     get_histogram_js = 'statsCollectionController.getBrowserHistogram("%s")'
 
     for display_name, histogram_name in self.HISTOGRAMS_TO_RECORD.iteritems():
       result = tab.EvaluateJavaScript(get_histogram_js % histogram_name)
       result = json.loads(result)
       measured_time = 0
 
       if 'sum' in result:
         # For all the histograms logged here, there's a single entry so sum
         # is the exact value for that entry.
         measured_time = result['sum']
       elif 'buckets' in result:
         measured_time = \
             (result['buckets'][0]['high'] + result['buckets'][0]['low']) / 2
 
       results.Add(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)