Update perf page_set to use story_set

tools/perf/page_sets/throttled_plugins.py

Index: tools/perf/page_sets/throttled_plugins.py
diff --git a/tools/perf/page_sets/throttled_plugins.py b/tools/perf/page_sets/throttled_plugins.py
index 91ce470e19215794d06b2bc9529cb80bf48f07a2..0de8546606fb0734054e7ab4dfe074fca4620b42 100644
--- a/tools/perf/page_sets/throttled_plugins.py
+++ b/tools/perf/page_sets/throttled_plugins.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 ThrottledPluginsPageSet(page_set.PageSet):
+class ThrottledPluginsPageSet(story.StorySet):
   def __init__(self):
     super(ThrottledPluginsPageSet, self).__init__(
         archive_data_file='data/throttled_plugins.json',
-        bucket=page_set.PUBLIC_BUCKET)
+        cloud_storage_bucket=story.PUBLIC_BUCKET)
     urls_with_throttled_plugins = [
         'http://cnn.com',
         'http://techcrunch.com',