Update perf page_set to use story_set

tools/perf/page_sets/tough_path_rendering_cases.py

Index: tools/perf/page_sets/tough_path_rendering_cases.py
diff --git a/tools/perf/page_sets/tough_path_rendering_cases.py b/tools/perf/page_sets/tough_path_rendering_cases.py
index b603aae6f387d9c60dfe259d9aaf808cbc5a5dc0..7dca1bc66e10d7d187909aa36d56adb75aa71193 100644
--- a/tools/perf/page_sets/tough_path_rendering_cases.py
+++ b/tools/perf/page_sets/tough_path_rendering_cases.py
@@ -1,8 +1,8 @@
 # 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 telemetry import story
 from telemetry.page import page as page_module
-from telemetry.page import page_set as page_set_module
 
 
 class ToughPathRenderingCasesPage(page_module.Page):
@@ -20,7 +20,7 @@ class ChalkboardPage(page_module.Page):
           'document.getElementById("StartButton").click()')
       action_runner.Wait(20)
 
-class ToughPathRenderingCasesPageSet(page_set_module.PageSet):
+class ToughPathRenderingCasesPageSet(story.StorySet):
 
   """
   Description: Self-driven path rendering examples
@@ -29,7 +29,7 @@ class ToughPathRenderingCasesPageSet(page_set_module.PageSet):
   def __init__(self):
     super(ToughPathRenderingCasesPageSet, self).__init__(
       archive_data_file='data/tough_path_rendering_cases.json',
-      bucket=page_set_module.PARTNER_BUCKET)
+      cloud_storage_bucket=story.PARTNER_BUCKET)
 
     urls_list = [
       'http://www.craftymind.com/factory/guimark2/HTML5ChartingTest.html'