[tools/perf] Reference legacy_page_test module instead of page_test

tools/perf/measurements/memory.py

 # Copyright 2012 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 logging
 
-from telemetry.page import page_test
+from telemetry.page import legacy_page_test
 
 from metrics import memory
 from metrics import power
 
 
-class Memory(page_test.PageTest):
+class Memory(legacy_page_test.LegacyPageTest):
 
   def __init__(self):
     super(Memory, self).__init__()
     self._memory_metric = None
     self._power_metric = None
 
   def WillStartBrowser(self, platform):
     self._power_metric = power.PowerMetric(platform)
 
   def DidStartBrowser(self, browser):
@@ skipping 15 matching lines @@
   def ValidateAndMeasurePage(self, page, tab, results):
     self._power_metric.Stop(page, tab)
     self._memory_metric.Stop(page, tab)
     self._memory_metric.AddResults(tab, results)
     self._power_metric.AddResults(tab, results)
 
   def DidRunPage(self, platform):
     # TODO(rnephew): Remove when crbug.com/553601 is solved.
     logging.info('DidRunPage for memory metric')
     self._power_metric.Close()