Update perf page_set to use story_set

tools/perf/page_sets/tough_scheduling_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 ToughSchedulingCasesPage(page_module.Page):
 
   def __init__(self, url, page_set):
     super(ToughSchedulingCasesPage, self).__init__(
         url=url, page_set=page_set, credentials_path='data/credentials.json',
         shared_page_state_class=shared_page_state.SharedMobilePageState)
     self.archive_data_file = 'data/tough_scheduling_cases.json'
@@ skipping 366 matching lines @@
     with action_runner.CreateGestureInteraction('LoadAction'):
       action_runner.ExecuteJavaScript('kickOffLoading()')
       action_runner.WaitForJavaScriptCondition('window.__ready')
       # Click one second after the resources have finished loading.
       action_runner.Wait(1)
       action_runner.TapElement(selector='input[id="run"]')
       # Wait for the test to complete.
       action_runner.WaitForJavaScriptCondition('window.__finished')
 
 
-class ToughSchedulingCasesPageSet(page_set_module.PageSet):
+class ToughSchedulingCasesPageSet(story.StorySet):
 
   """Tough scheduler latency test cases."""
 
   def __init__(self):
     super(ToughSchedulingCasesPageSet, self).__init__(
         archive_data_file='data/tough_scheduling_cases.json',
-        bucket=page_set_module.INTERNAL_BUCKET)
+        cloud_storage_bucket=story.INTERNAL_BUCKET)
 
     # Why: Simple scrolling baseline
     self.AddUserStory(ToughSchedulingCasesPage(
         'file://tough_scheduling_cases/simple_text_page.html',
         self))
     self.AddUserStory(Page1(self))
     self.AddUserStory(Page2(self))
     self.AddUserStory(Page3(self))
     self.AddUserStory(Page4(self))
     # Disabled until crbug.com/413829 is fixed.
@@ skipping 80 matching lines @@
         desktop=True,
         slow_handler=True,
         bounce=True,
         page_set=self))
     # Why: For measuring the latency of scroll-synchronized effects.
     self.AddUserStory(SynchronizedScrollOffsetPage(page_set=self))
     # Why: Test loading a large amount of Javascript.
     self.AddUserStory(SecondBatchJsPage(page_set=self, variant='light'))
     self.AddUserStory(SecondBatchJsPage(page_set=self, variant='medium'))
     self.AddUserStory(SecondBatchJsPage(page_set=self, variant='heavy'))