[Telemetry] Implement dirty profile generation

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 18 matching lines @@
     for i in xrange(1, len(page.page_set.pages)):
       t = tab.browser.tabs.New()
 
       page_state = page_runner.PageState()
       page_state.PreparePage(page.page_set.pages[i], t)
       page_state.ImplicitPageNavigation(page.page_set.pages[i], t)
 
   def MeasurePage(self, _, tab, results):
     """Although this is called MeasurePage, we're actually using this function
     to cycle through each tab that was opened via DidNavigateToPage and
-    thenrecord a single histogram for the tab switching metric.
+    then record a single histogram for the tab switching metric.
     """
     histogram_name = 'MPArch.RWH_TabSwitchPaintDuration'
     histogram_type = histogram_util.BROWSER_HISTOGRAM
     first_histogram = histogram_util.GetHistogramFromDomAutomation(
         histogram_type, histogram_name, tab)
     prev_histogram = first_histogram
 
     for i in xrange(len(tab.browser.tabs)):
       t = tab.browser.tabs[i]
       t.Activate()
       def _IsDone():
         cur_histogram = histogram_util.GetHistogramFromDomAutomation(
             histogram_type, histogram_name, tab)
         diff_histogram = histogram_util.SubtractHistogram(
             cur_histogram, prev_histogram)
         return diff_histogram
       util.WaitFor(_IsDone, 30)
       prev_histogram = histogram_util.GetHistogramFromDomAutomation(
           histogram_type, histogram_name, tab)
 
     last_histogram = histogram_util.GetHistogramFromDomAutomation(
         histogram_type, histogram_name, tab)
     diff_histogram = histogram_util.SubtractHistogram(last_histogram,
         first_histogram)
 
     results.AddSummary(histogram_name, '', diff_histogram,
         data_type='unimportant-histogram')