Revert of Using multi-tab story in TabSwitching Benchmark

tools/perf/measurements/tab_switching.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.
 
 """The tab switching measurement.
 
 This measurement opens pages in different tabs. After all the tabs have opened,
 it cycles through each tab in sequence, and records a histogram of the time
 between when a tab was first requested to be shown, and when it was painted.
 Power usage is also measured.
 """
 
+import json
+import time
+
+from telemetry.core import util
 from telemetry.page import legacy_page_test
 from telemetry.value import histogram
 from telemetry.value import histogram_util
 
 from metrics import keychain_metric
+from metrics import power
+
+# TODO: Revisit this test once multitab support is finalized.
 
 
 class TabSwitching(legacy_page_test.LegacyPageTest):
+
+  # Amount of time to measure, in seconds.
+  SAMPLE_TIME = 30
+
   def __init__(self):
     super(TabSwitching, self).__init__()
-    self._first_histogram = None
+    self.first_page_in_storyset = True
+    self._power_metric = None
 
   def CustomizeBrowserOptions(self, options):
     keychain_metric.KeychainMetric.CustomizeBrowserOptions(options)
 
-    options.AppendExtraBrowserArgs(['--enable-stats-collection-bindings'])
+    options.AppendExtraBrowserArgs([
+        '--enable-stats-collection-bindings'
+    ])
+    # Enable background networking so we can test its impact on power usage.
+    options.disable_background_networking = False
+    power.PowerMetric.CustomizeBrowserOptions(options)
 
-  @classmethod
-  def _GetTabSwitchHistogram(cls, tab_to_switch):
+  def WillStartBrowser(self, platform):
+    self.first_page_in_storyset = True
+    self._power_metric = power.PowerMetric(platform, TabSwitching.SAMPLE_TIME)
+
+  def TabForPage(self, page, browser):
+    del page  # unused
+    if self.first_page_in_storyset:
+      # The initial browser window contains a single tab, navigate that tab
+      # rather than creating a new one.
+      self.first_page_in_storyset = False
+      return browser.tabs[0]
+
+    return browser.tabs.New()
+
+  def StopBrowserAfterPage(self, browser, page):
+    # Restart the browser after the last page in the pageset.
+    return len(browser.tabs) >= len(page.story_set.stories)
+
+  def ValidateAndMeasurePage(self, page, tab, results):
+    """On the last tab, cycle through each tab that was opened and then record
+    a single histogram for the tab switching metric."""
+    browser = tab.browser
+    if len(browser.tabs) != len(page.story_set.stories):
+      return
+
+    if browser.tabs < 2:
+      raise Exception('Should have at least two tabs for tab switching')
+
+    # Measure power usage of tabs after quiescence.
+    util.WaitFor(tab.HasReachedQuiescence, 60)
+
+    if browser.platform.CanMonitorPower():
+      self._power_metric.Start(page, tab)
+      time.sleep(TabSwitching.SAMPLE_TIME)
+      self._power_metric.Stop(page, tab)
+      self._power_metric.AddResults(tab, results,)
+
     histogram_name = 'MPArch.RWH_TabSwitchPaintDuration'
     histogram_type = histogram_util.BROWSER_HISTOGRAM
-    return histogram_util.GetHistogram(
-        histogram_type, histogram_name, tab_to_switch)
+    display_name = 'MPArch_RWH_TabSwitchPaintDuration'
+    first_histogram = histogram_util.GetHistogram(
+        histogram_type, histogram_name, tab)
+    prev_histogram = first_histogram
 
-  def DidNavigateToPage(self, page, tab):
-    """record the starting histogram"""
-    self._first_histogram = self._GetTabSwitchHistogram(tab)
+    for tab_to_switch in browser.tabs:
+      tab_to_switch.Activate()
+      def _IsDone():
+        # pylint: disable=W0640
+        cur_histogram = histogram_util.GetHistogram(
+            histogram_type, histogram_name, tab_to_switch)
+        diff_histogram = histogram_util.SubtractHistogram(
+            cur_histogram, prev_histogram)
+        # TODO(deanliao): Add SubtractHistogramRawValue to process histogram
+        #     object instead of JSON string.
+        diff_histogram_count = json.loads(diff_histogram).get('count', 0)
+        return diff_histogram_count > 0
+      util.WaitFor(_IsDone, 30)
 
-  def ValidateAndMeasurePage(self, page, tab, results):
-    """record the ending histogram for the tab switching metric."""
-    last_histogram = self._GetTabSwitchHistogram(tab)
+      # We need to get histogram again instead of getting cur_histogram as
+      # variables modified inside inner function cannot be retrieved. However,
+      # inner function can see external scope's variables.
+      prev_histogram = histogram_util.GetHistogram(
+          histogram_type, histogram_name, tab_to_switch)
+
+    last_histogram = prev_histogram
     total_diff_histogram = histogram_util.SubtractHistogram(last_histogram,
-                            self._first_histogram)
-
-    display_name = 'MPArch_RWH_TabSwitchPaintDuration'
+                                                            first_histogram)
     results.AddSummaryValue(
         histogram.HistogramValue(None, display_name, 'ms',
-            raw_value_json=total_diff_histogram,
-            important=False))
+                                 raw_value_json=total_diff_histogram,
+                                 important=False))
 
     keychain_metric.KeychainMetric().AddResults(tab, results)
+
+  def DidRunPage(self, platform):
+    del platform  # unused
+    self._power_metric.Close()