Update perf page_set to use story_set

tools/perf/page_sets/gmail_refresh.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 import story
+from telemetry.page import page as page_module
 from telemetry.page import shared_page_state
-from telemetry.page import page as page_module
-from telemetry.page import page_set as page_set_module
 
 
 class GmailRefreshPage(page_module.Page):
 
   """ Why: Continually reload the gmail page. """
 
   def __init__(self, page_set):
     super(GmailRefreshPage, self).__init__(
       url='https://mail.google.com/mail/',
       shared_page_state_class=shared_page_state.SharedDesktopPageState,
       page_set=page_set, credentials_path = 'data/credentials.json')
     self.credentials = 'google'
     self.archive_data_file = 'data/gmail_refresh.json'
 
   def RunEndure(self, action_runner):
     action_runner.ReloadPage()
 
 
-class GmailRefreshPageSet(page_set_module.PageSet):
+class GmailRefreshPageSet(story.StorySet):
 
   """
   Description: Chrome Endure control test to test gmail page reload
   """
 
   def __init__(self):
     super(GmailRefreshPageSet, self).__init__(
       archive_data_file='data/gmail_refresh.json',
-      bucket=page_set_module.PUBLIC_BUCKET)
+      cloud_storage_bucket=story.PUBLIC_BUCKET)
 
     self.AddUserStory(GmailRefreshPage(self))