mac: Expose keychain access frequency to Telemetry.

tools/perf/measurements/polymer_load.py

 # Copyright 2014 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.
 
+from measurements import PageTestMeasurement
 from telemetry.page import page
-from telemetry.page import page_test
 from telemetry.value import scalar
 
 
 class PageForPolymerLoad(page.Page):
 
   def __init__(self, url, page_set, ready_event='polymer-ready'):
     super(PageForPolymerLoad, self).__init__(
       url=url,
       page_set=page_set)
     self.script_to_evaluate_on_commit = '''
       document.addEventListener("%s", function() {
         var unused = document.body.offsetHeight;
         window.__polymer_ready_time = performance.now();
         setTimeout(function() {
           window.__polymer_ready = true;
         }, 1000);
       })
     ''' % ready_event
 
   def RunNavigateSteps(self, action_runner):
     action_runner.NavigateToPage(self)
     action_runner.WaitForJavaScriptCondition('window.__polymer_ready')
 
 
-class PolymerLoadMeasurement(page_test.PageTest):
+class PolymerLoadMeasurement(PageTestMeasurement):
   def ValidateAndMeasurePage(self, _, tab, results):
+    super(PolymerLoadMeasurement, self).ValidateAndMeasurePage(
+        page, tab, results)
     result = int(tab.EvaluateJavaScript('__polymer_ready_time'))
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'Total', 'ms', result))