[telemetry] Move tab from RunState to PageState.

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.
 """
@@ skipping 10 matching lines @@
 class TabSwitching(page_measurement.PageMeasurement):
   def __init__(self):
     super(TabSwitching, self).__init__()
     self._cpu_metric = None
 
   def CustomizeBrowserOptions(self, options):
     options.AppendExtraBrowserArgs([
         '--enable-stats-collection-bindings'
     ])
 
-  def TabForPage(self, page, tab):
-    return tab.browser.tabs.New()
+  def TabForPage(self, page, browser):
+    return browser.tabs.New()
 
   def DidStartBrowser(self, browser):
     self._cpu_metric = cpu.CpuMetric(browser)
 
   def MeasurePage(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."""
     if len(tab.browser.tabs) != len(page.page_set.pages):
       return
     self._cpu_metric.Start(page, tab)
@@ skipping 22 matching lines @@
       prev_histogram = histogram_util.GetHistogram(
           histogram_type, histogram_name, tab)
 
     last_histogram = histogram_util.GetHistogram(
         histogram_type, histogram_name, tab)
     diff_histogram = histogram_util.SubtractHistogram(last_histogram,
         first_histogram)
 
     results.AddSummary(histogram_name, '', diff_histogram,
         data_type='unimportant-histogram')