Update perf page_set to use story_set

tools/perf/page_sets/top_desktop_sites_2012Q3.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
-from telemetry.page import page_set
-
 
 TOP_2013_URLS = [
   'http://www.facebook.com/barackobama',
   'https://www.google.com/search?q=barack%20obama',
   'http://youtube.com',
   'http://yahoo.com',
   'http://www.baidu.com/s?wd=barack+obama',
   'http://en.wikipedia.org/wiki/Wikipedia',
   'http://qq.com',
   'http://www.amazon.com/Kindle-Fire-Amazon-Tablet/dp/B0051VVOB2',
@@ skipping 234 matching lines @@
   def __init__(self, url, ps):
     super(Top2012Q3Page, self).__init__(
         url=url, page_set=ps, credentials_path = 'data/credentials.json')
     self.archive_data_file = 'data/2012Q3.json'
 
   def RunPageInteractions(self, action_runner):
     with action_runner.CreateGestureInteraction('ScrollAction'):
       action_runner.ScrollPage()
 
 
-class Top2012Q3PageSet(page_set.PageSet):
+class Top2012Q3PageSet(story.StorySet):
   """ Pages hand-picked from top-lists in Q32012. """
 
   def __init__(self):
     super(Top2012Q3PageSet, self).__init__(
       archive_data_file='data/2012Q3.json',
-      bucket=page_set.PARTNER_BUCKET)
+      cloud_storage_bucket=story.PARTNER_BUCKET)
 
 
     for url in TOP_2013_URLS:
       self.AddUserStory(Top2012Q3Page(url, self))