Migrate from telemetry PageSet -> StorySet.

tools/chrome_proxy/integration_tests/chrome_proxy_pagesets/safebrowsing.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.
 import logging
 
 from telemetry.core import exceptions
 from telemetry.page import page as page_module
-from telemetry.page import page_set as page_set_module
+from telemetry import story
 
 
 class SafebrowsingPage(page_module.Page):
 
   """
   Why: Expect 'malware ahead' page. Use a short navigation timeout because no
   response will be received.
   """
 
   def __init__(self, url, page_set, expect_timeout):
     super(SafebrowsingPage, self).__init__(url=url, page_set=page_set)
     self._expect_timeout = expect_timeout
 
   def RunNavigateSteps(self, action_runner):
     try:
       action_runner.Navigate(self.url, timeout_in_seconds=5)
     except exceptions.TimeoutException as e:
       if self._expect_timeout:
         logging.warning('Navigation timeout on page %s', self.url)
       else:
         raise e
 
 
-class SafebrowsingPageSet(page_set_module.PageSet):
+class SafebrowsingStorySet(story.StorySet):
 
   """ Chrome proxy test sites """
 
   def __init__(self, expect_timeout=False):
-    super(SafebrowsingPageSet, self).__init__()
+    super(SafebrowsingStorySet, self).__init__()
 
-    self.AddUserStory(
+    self.AddStory(
         SafebrowsingPage('http://www.ianfette.org/', self, expect_timeout))