Update perf page_set to use story_set

tools/perf/page_sets/service_worker.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
-from telemetry.page import page_set as page_set
-
 
 archive_data_file_path = 'data/service_worker.json'
 
 
-class ServiceWorkerPageSet(page_set.PageSet):
+class ServiceWorkerPageSet(story.StorySet):
   """Page set of applications using ServiceWorker"""
 
   def __init__(self):
     super(ServiceWorkerPageSet, self).__init__(
         archive_data_file=archive_data_file_path,
-        bucket=page_set.PARTNER_BUCKET)
+        cloud_storage_bucket=story.PARTNER_BUCKET)
 
     # Why: the first application using ServiceWorker
     # 1st time: registration
     self.AddUserStory(page.Page(
         'https://jakearchibald.github.io/trained-to-thrill/', self,
         name='first_load', make_javascript_deterministic=False))
     # 2st time: 1st onfetch with caching
     self.AddUserStory(page.Page(
         'https://jakearchibald.github.io/trained-to-thrill/', self,
         name='second_load', make_javascript_deterministic=False))
     # 3rd time: 2nd onfetch from cache
     self.AddUserStory(page.Page(
         'https://jakearchibald.github.io/trained-to-thrill/', self,
         name='third_load', make_javascript_deterministic=False))