Update perf page_set to use story_set

tools/perf/page_sets/top_25_pages.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 page_sets import top_pages
+from telemetry import story
+from telemetry.page import page
 from telemetry.page import shared_page_state
-from telemetry.page import page
-from telemetry.page import page_set
-
-from page_sets import top_pages
 
 
-class Top25PageSet(page_set.PageSet):
+class Top25PageSet(story.StorySet):
 
   """ Page set consists of top 25 pages with only navigation actions. """
 
   def __init__(self):
     super(Top25PageSet, self).__init__(
         archive_data_file='data/top_25.json',
-        bucket=page_set.PARTNER_BUCKET)
+        cloud_storage_bucket=story.PARTNER_BUCKET)
 
     shared_desktop_state = shared_page_state.SharedDesktopPageState
     self.AddUserStory(top_pages.GoogleWebSearchPage(self, shared_desktop_state))
     self.AddUserStory(top_pages.GmailPage(self, shared_desktop_state))
     self.AddUserStory(top_pages.GoogleCalendarPage(self, shared_desktop_state))
     self.AddUserStory(
         top_pages.GoogleImageSearchPage(self, shared_desktop_state))
     self.AddUserStory(top_pages.GoogleDocPage(self, shared_desktop_state))
     self.AddUserStory(top_pages.GooglePlusPage(self, shared_desktop_state))
     self.AddUserStory(top_pages.YoutubePage(self, shared_desktop_state))
@@ skipping 24 matching lines @@
         'http://answers.yahoo.com',
         # Why: #1 Alexa sports
         'http://sports.yahoo.com/',
         # Why: top tech blog
         'http://techcrunch.com'
     ]
 
     for url in other_urls:
       self.AddUserStory(
           page.Page(url, self, shared_page_state_class=shared_desktop_state))