Add Multi-tab System Health Story

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 dd64dfa0d2f583d17afc72b67146ef3b9351c045..5a6e1c3fea85232aba45ed17a1db5f4833197328 100644
--- a/tools/perf/measurements/tab_switching.py
+++ b/tools/perf/measurements/tab_switching.py
@@ -10,10 +10,8 @@ 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
@@ -21,6 +19,7 @@ from telemetry.value import histogram_util
 from metrics import keychain_metric
 from metrics import power
 
+
 # TODO: Revisit this test once multitab support is finalized.
 
 
@@ -33,6 +32,7 @@ class TabSwitching(legacy_page_test.LegacyPageTest):
     super(TabSwitching, self).__init__()
     self.first_page_in_storyset = True
     self._power_metric = None
+    self._first_histogram = None
 
   def CustomizeBrowserOptions(self, options):
     keychain_metric.KeychainMetric.CustomizeBrowserOptions(options)
@@ -45,76 +45,35 @@ class TabSwitching(legacy_page_test.LegacyPageTest):
     power.PowerMetric.CustomizeBrowserOptions(options)
 
   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()
+  @classmethod
+  def _GetTabSwitchHistogram(cls, tab_to_switch):
+    histogram_name = 'MPArch.RWH_TabSwitchPaintDuration'
+    histogram_type = histogram_util.BROWSER_HISTOGRAM
+    return histogram_util.GetHistogram(
+        histogram_type, histogram_name, tab_to_switch)
 
-  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 DidNavigateToPage(self, page, tab):
+    """record the starting histogram"""
+    self._first_histogram = self._GetTabSwitchHistogram(tab)
 
   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():
+    """record the ending histogram for the tab switching metric."""
+    if tab.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
-    display_name = 'MPArch_RWH_TabSwitchPaintDuration'
-    first_histogram = histogram_util.GetHistogram(
-        histogram_type, histogram_name, tab)
-    prev_histogram = first_histogram
-
-    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)
-
-      # 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
+    last_histogram = self._GetTabSwitchHistogram(tab)
     total_diff_histogram = histogram_util.SubtractHistogram(last_histogram,
-                                                            first_histogram)
+                            self._first_histogram)
+    display_name = 'MPArch_RWH_TabSwitchPaintDuration'
     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)