[Android] Don't wait for background tabs

The session restore tests were timing out on Android. This was because
they were waiting for the background tabs to be loaded, which they
would not be in normal startup.

The only reason the test worked at all is that when devtools accessed
the background tabs this forced them to be loaded.

This changes the test to only wait for, and to only measure, the
foreground tab.

NOTRY=true
BUG=343168,343900

Review URL: https://codereview.chromium.org/161473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251364 0039d316-1c4b-4281-b951-d872f2087c98

tools/perf/measurements/session_restore.py

@@ -50,11 +50,8 @@ class SessionRestore(startup.Startup):
     self._cpu_metric.Start(None, None)
 
   def MeasurePage(self, page, tab, results):
-    # Wait for all tabs to finish loading.
-    for i in xrange(len(tab.browser.tabs)):
-      t = tab.browser.tabs[i]
-      t.WaitForDocumentReadyStateToBeComplete()
 
+    tab.browser.foreground_tab.WaitForDocumentReadyStateToBeComplete()
     # Record CPU usage from browser start to when all pages have loaded.
     self._cpu_metric.Stop(None, None)
     self._cpu_metric.AddResults(tab, results, 'cpu_utilization')

tools/perf/metrics/startup_metric.py

@@ -41,17 +41,15 @@ class StartupMetric(Metric):
       return None
     return (int(high_bytes) << 32) | (int(low_bytes) << 1)
 
-  # 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):
+        ['load_start_ms', 'load_duration_ms'])
+
+    def RecordTabLoadTime(t):
       try:
-        t = tab.browser.tabs[i]
         t.WaitForDocumentReadyStateToBeComplete()
 
         result = t.EvaluateJavaScript(
@@ -61,51 +59,34 @@ class StartupMetric(Metric):
         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           raise Exception("Outdated Chrome version, "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))
+            int(result['load_duration_ms'])))
       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()
-
-    if 'android' in tab.browser.browser_type:
-      # document.hidden is broken on Android - crbug.com/322544.
-      foreground_tab_stats = [tab_load_times[0]]
-    else:
-      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]
-
-    # Report load stats.
+        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)
-
     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)
-
   def AddResults(self, tab, results):
     get_histogram_js = 'statsCollectionController.getBrowserHistogram("%s")'
 

tools/telemetry/telemetry/core/browser.py

@@ -84,6 +84,18 @@ class Browser(object):
   def tabs(self):
     return self._tabs
 
+  @property
+  def foreground_tab(self):
+    for i in xrange(len(self._tabs)):
+      # The foreground tab is the first (only) one that isn't hidden.
+      # This only works through luck on Android, due to crbug.com/322544
+      # which means that tabs that have never been in the foreground return
+      # document.hidden as false; however in current code the Android foreground
+      # tab is always tab 0, which will be the first one that isn't hidden
+      if self._tabs[i].EvaluateJavaScript('!document.hidden'):
+        return self._tabs[i]
+    raise Exception("No foreground tab found")
+
   @property
   def extensions(self):
     """Returns the extension dictionary if it exists."""
@@ -392,3 +404,4 @@ class Browser(object):
 
        See the documentation of the SystemInfo class for more details."""
     return self._browser_backend.GetSystemInfo()
+