[tools/perf] Reference legacy_page_test module instead of page_test

tools/perf/measurements/webrtc.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 telemetry.page import page_test
+from telemetry.page import legacy_page_test
 
 from metrics import cpu
 from metrics import media
 from metrics import memory
 from metrics import power
 from metrics import webrtc_stats
 
 
-class WebRTC(page_test.PageTest):
+class WebRTC(legacy_page_test.LegacyPageTest):
   """Gathers WebRTC-related metrics on a page set."""
 
   def __init__(self):
     super(WebRTC, self).__init__()
     self._cpu_metric = None
     self._media_metric = None
     self._memory_metric = None
     self._power_metric = None
     self._webrtc_stats_metric = None
 
@@ skipping 34 matching lines @@
     self._memory_metric.AddResults(tab, results)
 
     self._power_metric.Stop(page, tab)
     self._power_metric.AddResults(tab, results)
 
     self._webrtc_stats_metric.Stop(page, tab)
     self._webrtc_stats_metric.AddResults(tab, results)
 
   def DidRunPage(self, platform):
     self._power_metric.Close()