[tools/perf] Reference legacy_page_test module instead of page_test

tools/perf/measurements/v8_detached_context_age_in_gc.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.
 
 import json
 
-from telemetry.page import page_test
+from telemetry.page import legacy_page_test
 from telemetry.value import histogram_util
 from telemetry.value import scalar
 from telemetry.value import skip
 
 _NAME = 'V8.DetachedContextAgeInGC'
 _UNITS = 'garbage_collections'
 _DISPLAY_NAME = 'V8_DetachedContextAgeInGC'
 _TYPE = histogram_util.RENDERER_HISTOGRAM
 _DESCRIPTION = 'Number of GCs needed to collect detached context'
 
 
 def _GetMaxDetachedContextAge(tab, data_start):
   data = histogram_util.GetHistogram(_TYPE, _NAME, tab)
   delta = histogram_util.SubtractHistogram(data, data_start)
   if not 'buckets' in delta:
     return
   buckets = json.loads(delta)['buckets']
   if buckets:
     return max(x.get('high', x['low']) for x in buckets)
 
 
-class V8DetachedContextAgeInGC(page_test.PageTest):
+class V8DetachedContextAgeInGC(legacy_page_test.LegacyPageTest):
 
   def __init__(self):
     super(V8DetachedContextAgeInGC, self).__init__()
     self._data_start = None
 
   def CustomizeBrowserOptions(self, options):
     options.AppendExtraBrowserArgs(['--enable-stats-collection-bindings'])
 
   def DidNavigateToPage(self, page, tab):
     self._data_start = histogram_util.GetHistogram(_TYPE, _NAME, tab)
 
   def ValidateAndMeasurePage(self, page, tab, results):
     # Trigger GC to get histogram data.
     # Seven GCs should be enough to collect any detached context.
     # If a detached context survives more GCs then there is a leak.
     MAX_AGE = 8
     for _ in xrange(MAX_AGE):
       tab.CollectGarbage()
     value = _GetMaxDetachedContextAge(tab, self._data_start)
     if value is None:
       results.AddValue(skip.SkipValue(
           results.current_page, 'No detached contexts'))
     else:
       results.AddValue(scalar.ScalarValue(
           results.current_page, _DISPLAY_NAME, _UNITS, value,
           description=_DESCRIPTION))