Update perf page_set to use story_set

tools/perf/page_sets/tough_energy_cases.py

Index: tools/perf/page_sets/tough_energy_cases.py
diff --git a/tools/perf/page_sets/tough_energy_cases.py b/tools/perf/page_sets/tough_energy_cases.py
index e819561894ab4aace484f5dc34bb9ed730ee1e26..f7ce7cef110585bb9e9fda90620d7c42d7b91e6b 100644
--- a/tools/perf/page_sets/tough_energy_cases.py
+++ b/tools/perf/page_sets/tough_energy_cases.py
@@ -1,8 +1,8 @@
 # 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
 
 
 class ToughEnergyCasesPage(page_module.Page):
@@ -33,13 +33,13 @@ class GooglePage(ToughEnergyCasesPage):
         'document.getElementById("gb") !== null')
 
 
-class ToughEnergyCasesPageSet(page_set_module.PageSet):
+class ToughEnergyCasesPageSet(story.StorySet):
   """Pages for measuring Chrome power draw."""
 
   def __init__(self):
     super(ToughEnergyCasesPageSet, self).__init__(
         archive_data_file='data/tough_energy_cases.json',
-        bucket=page_set_module.PARTNER_BUCKET)
+        cloud_storage_bucket=story.PARTNER_BUCKET)
 
     # TODO: this part of the test is disabled because it fails when
     # run with replay data and not with live data.  See crbug.com/465692