[tools/perf] Reference legacy_page_test module instead of page_test

tools/perf/measurements/startup.py

 # Copyright 2013 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 keychain_metric
 from metrics import startup_metric
 
 
-class Startup(page_test.PageTest):
+class Startup(legacy_page_test.LegacyPageTest):
   """Performs a measurement of Chromium's startup performance.
 
   Uses cold start if cold==True, otherwise uses warm start. A cold start means
   none of the Chromium files are in the disk cache. A warm start assumes the OS
   has already cached much of Chromium's content. For warm tests, you should
   repeat the page set to ensure it's cached.
   """
 
   def __init__(self, cold=False):
     super(Startup, self).__init__(needs_browser_restart_after_each_page=True)
@@ skipping 19 matching lines @@
   none of the Chromium files are in the disk cache. A warm start assumes the OS
   has already cached much of Chromium's content. For warm tests, you should
   repeat the page set to ensure it's cached.
 
   The startup URL is taken from the page's startup_url. This
   allows the testing of multiple different URLs in a single benchmark.
   """
 
   def __init__(self, cold=False):
     super(StartWithUrl, self).__init__(cold=cold)