Update perf page_set to use story_set

tools/perf/page_sets/plugin_power_saver.py

Index: tools/perf/page_sets/plugin_power_saver.py
diff --git a/tools/perf/page_sets/plugin_power_saver.py b/tools/perf/page_sets/plugin_power_saver.py
index 61a62b09c68d42becda5e9fac5d0f574a5ce417b..be31ce75ff369c23fa263917b0c50ba7df549407 100644
--- a/tools/perf/page_sets/plugin_power_saver.py
+++ b/tools/perf/page_sets/plugin_power_saver.py
@@ -1,16 +1,16 @@
 # 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.page import shared_page_state
+from telemetry import story
 from telemetry.page import page
-from telemetry.page import page_set
+from telemetry.page import shared_page_state
 
 
-class PluginPowerSaverPageSet(page_set.PageSet):
+class PluginPowerSaverPageSet(story.StorySet):
   def __init__(self):
     super(PluginPowerSaverPageSet, self).__init__(
         archive_data_file='data/plugin_power_saver.json',
-        bucket=page_set.PUBLIC_BUCKET)
+        cloud_storage_bucket=story.PUBLIC_BUCKET)
     self.AddUserStory(page.Page(
         'http://a.tommycli.com/small_only.html',
         page_set=self,