[tools/perf] Prepare V8DetachedContextAgeInGCTests for JS API migration

tools/perf/measurements/v8_detached_context_age_in_gc_unittest.py

 # Copyright 2015 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 telemetry.internal.results import page_test_results
 from telemetry.page import page as page_module
 from telemetry.testing import options_for_unittests
 from telemetry.testing import page_test_test_case
 from telemetry.util import wpr_modes
 
 from measurements import v8_detached_context_age_in_gc
 
 
 class FakePage(page_module.Page):
 
   def __init__(self, url):
     super(FakePage, self).__init__(url=url)
 
   @property
   def is_file(self):
     return self._url.startswith('file://')
 
 
 class FakeTab(object):
 
   def __init__(self, histograms):
     self.histograms = histograms
     self.current_histogram_index = 0
 
-  def EvaluateJavaScript(self, script):
-    if 'V8.DetachedContextAgeInGC' in script:
+  def EvaluateJavaScript(self, script, **kwargs):
+    histogram_name = 'V8.DetachedContextAgeInGC'
+    if kwargs.get('name') == histogram_name or histogram_name in script:

[perezju, 2017/02/14 11:42:04]

Tweaked to work both before and after applying the change in:
https://codereview.chromium.org/2687773003/diff/40001/telemetry/telemetry/val...

       self.current_histogram_index += 1
       return self.histograms[self.current_histogram_index - 1]
     return '{}'
 
+  # TODO(catapult:3028): Remove after migration to new JS API completed.
+  def EvaluateJavaScript2(self, script, **kwargs):
+    return self.EvaluateJavaScript(script, **kwargs)
+
   def CollectGarbage(self):
     pass
 
 
 def _MeasureFakePage(histograms):
   results = page_test_results.PageTestResults()
   page = FakePage('file://blank.html')
   tab = FakeTab(histograms)
   metric = v8_detached_context_age_in_gc.V8DetachedContextAgeInGC()
   results.WillRunPage(page)
@@ skipping 49 matching lines @@
   def testWithSimplePage(self):
     page_set = self.CreateEmptyPageSet()
     page = SimplePage(page_set)
     page_set.AddStory(page)
     metric = v8_detached_context_age_in_gc.V8DetachedContextAgeInGC()
     results = self.RunMeasurement(metric, page_set, options=self._options)
     self.assertEquals(0, len(results.failures), msg=str(results.failures))
     actual = _ActualValues(results)['V8_DetachedContextAgeInGC']
     self.assertLessEqual(0, actual.value)
     self.assertEqual('garbage_collections', actual.units)