Revert of Using multi-tab story in TabSwitching Benchmark

tools/perf/measurements/tab_switching.py

Index: tools/perf/measurements/tab_switching.py
diff --git a/tools/perf/measurements/tab_switching.py b/tools/perf/measurements/tab_switching.py
index 5b8868e85d5e26e64424170b9445e0c2cf920aa7..dd64dfa0d2f583d17afc72b67146ef3b9351c045 100644
--- a/tools/perf/measurements/tab_switching.py
+++ b/tools/perf/measurements/tab_switching.py
@@ -10,44 +10,114 @@
 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()