[Telemetry]: Assert that page measurement results don't contain a '.' in their name.

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 30 matching lines @@
       return
     self._cpu_metric.Start(page, tab)
     time.sleep(.5)
     self._cpu_metric.Stop(page, tab)
     # Calculate the idle cpu load before any actions are done.
     self._cpu_metric.AddResults(tab, results,
                                 'idle_cpu_utilization')
 
     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 i in xrange(len(tab.browser.tabs)):
       t = tab.browser.tabs[i]
       t.Activate()
       def _IsDone():
         cur_histogram = histogram_util.GetHistogram(
             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.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,
+    results.AddSummary(display_name, '', diff_histogram,
         data_type='unimportant-histogram')