Revert of Re-subimission of https://codereview.chromium.org/1041213003/

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 d275fb78ed2099d49ad032801886335c7bdaa4ff..0a532affb1f4788beae79109679333d19af337b3 100644
--- a/tools/perf/metrics/startup_metric.py
+++ b/tools/perf/metrics/startup_metric.py
@@ -14,9 +14,6 @@
 
 class StartupMetric(Metric):
   "A metric for browser startup time."
-
-  # Seconds to wait for page loading complete.
-  DEFAULT_LOADING_TIMEOUT = 90
 
   HISTOGRAMS_TO_RECORD = {
     'messageloop_start_time' :
@@ -47,34 +44,36 @@
 
   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',
-        ['request_start_ms', 'load_end_ms'])
+        ['load_start_ms', 'load_duration_ms', 'request_start_ms'])
 
-    def RecordOneTab(t):
-      def EvaluateInt(exp):
-        val = t.EvaluateJavaScript(exp)
-        if not val:
-          logging.warn('%s undefined' % exp)
-          return 0
-        return int(val)
+    def RecordTabLoadTime(t):
+      try:
+        t.WaitForDocumentReadyStateToBeComplete()
 
-      try:
-        t.WaitForJavaScriptExpression(
-            'window.performance.timing["loadEventEnd"] > 0',
-            self.DEFAULT_LOADING_TIMEOUT)
+        result = t.EvaluateJavaScript(
+            'statsCollectionController.tabLoadTiming()')
+        result = json.loads(result)
 
-        # EvaluateJavaScript(window.performance.timing) doesn't guarantee to
-        # return the desired javascript object (crbug/472603). It may return an
-        # empty object. However getting individual field works.
-        # The behavior depends on Webkit implementation on different platforms.
-        load_event_end = EvaluateInt(
-            'window.performance.timing["loadEventEnd"]')
-        request_start = EvaluateInt(
-            'window.performance.timing["requestStart"]')
+        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+          raise Exception("Outdated Chrome version, "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
 
-        return TabLoadTime(request_start, load_event_end)
+        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'])))
       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
@@ -86,18 +85,19 @@
     # 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.
-    foreground_tab_stats = RecordOneTab(tab.browser.foreground_tab)
 
-    if foreground_tab_stats:
-      foreground_tab_load_complete = (
-          foreground_tab_stats.load_end_ms - browser_main_entry_time_ms)
+    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)
+    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_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))
+          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")'