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

tools/perf/metrics/startup_metric.py

Index: tools/perf/metrics/startup_metric.py
diff --git a/tools/perf/metrics/startup_metric.py b/tools/perf/metrics/startup_metric.py
index af1e3fff5a326b65e596e6f9c420e162bf3d8836..dd04416a386d3170d44a3f955373b7d87bbf9232 100644
--- a/tools/perf/metrics/startup_metric.py
+++ b/tools/perf/metrics/startup_metric.py
@@ -47,23 +47,12 @@ class StartupMetric(Metric):
     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-          raise Exception("Outdated Chrome version, "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:
@@ -71,9 +60,8 @@ class StartupMetric(Metric):
           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
@@ -89,8 +77,8 @@ class StartupMetric(Metric):
     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))