Update perf page_set to use story_set

tools/perf/page_sets/tough_scrolling_while_zoomed_in_cases.py

 # Copyright 2015 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 diagonal_scrolling_supported_shared_state
-
+from telemetry import story
 from telemetry.page import page as page_module
-from telemetry.page import page_set as page_set_module
 
 
 class ToughScrollingWhileZoomedInCasesPage(page_module.Page):
 
   def __init__(self, url, page_set):
     super(ToughScrollingWhileZoomedInCasesPage, self).__init__(
         url=url,
         page_set=page_set,
         shared_page_state_class=(
             diagonal_scrolling_supported_shared_state.
@@ skipping 12 matching lines @@
     # Then start measurements
     with action_runner.CreateGestureInteraction('ScrollAction'):
       # And begin the diagonal scroll
       action_runner.ScrollPage(
           direction='downright',
           # 10,000 was chosen because it is fast enough to completely stress the
           # rasterization (on a Nexus 5) without saturating results.
           speed_in_pixels_per_second=10000)
 
 
-class ToughScrollingWhileZoomedInCasesPageSet(page_set_module.PageSet):
+class ToughScrollingWhileZoomedInCasesPageSet(story.StorySet):
   """
   Description: A collection of difficult scrolling tests
   """
 
   def __init__(self):
     super(ToughScrollingWhileZoomedInCasesPageSet, self).__init__(
         archive_data_file='data/tough_pinch_zoom_cases.json',
-        bucket=page_set_module.PARTNER_BUCKET)
+        cloud_storage_bucket=story.PARTNER_BUCKET)
 
     # The following urls were chosen because they tend to have >15%
     # mean_pixels_approximated at this scrolling speed.
     urls_list = [
         'file://tough_scrolling_cases/background_fixed.html',
         'file://tough_scrolling_cases/fixed_nonstacking.html',
         'file://tough_scrolling_cases/iframe_scrolls.html',
         'file://tough_scrolling_cases/wheel_div_prevdefault.html'
     ]
 
     for url in urls_list:
       self.AddUserStory(ToughScrollingWhileZoomedInCasesPage(url, self))