Update perf page_set to use story_set

tools/perf/page_sets/flash_energy_cases.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 page_set as page_set_module
 from telemetry.page import shared_page_state
 
 
 class FlashEnergyCasesPage(page_module.Page):
 
   def __init__(self, url, page_set):
     super(FlashEnergyCasesPage, self).__init__(
         url=url, page_set=page_set,
         shared_page_state_class=shared_page_state.SharedDesktopPageState)
     self.archive_data_file = 'data/flash_energy_cases.json'
 
 
-class FlashEnergyCasesPageSet(page_set_module.PageSet):
+class FlashEnergyCasesPageSet(story.StorySet):
 
   """ Pages with flash heavy content. """
 
   def __init__(self):
     super(FlashEnergyCasesPageSet, self).__init__(
       archive_data_file='data/flash_energy_cases.json',
-      bucket=page_set_module.PARTNER_BUCKET)
+      cloud_storage_bucket=story.PARTNER_BUCKET)
 
     urls_list = [
         # pylint: disable=C0301
         'http://v.qq.com/cover/d/dm9vn9cnsn2v2gx.html?ptag=v.newplaybutton.program.dpjd',
         'http://videos.huffingtonpost.com/politics/protesters-march-to-hong-kong-leaders-home-518476075',
         'http://nos.nl/video/712855-eerste-beelden-na-de-aanslag-in-canada.html',
         # Why: Large flash ad
         'http://forum.gazeta.pl/forum/f,17007,Polityka_i_Gospodarka.html',
         # Why: Multiple flash ads
         'http://tinypic.com/',
         'https://www.facebook.com/video.php?v=524346051035153&set=vb.134474600022302&type=2&theater'
     ]
 
     for url in urls_list:
       self.AddUserStory(FlashEnergyCasesPage(url, self))