Update perf page_set to use story_set

tools/perf/page_sets/new_tab_page.py

 # 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.
 import time
 
+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
 
 INTERACTION_NAME = 'Interaction.PageLoading'
 
 # How long to wait for the page to finish rendering.
 LOADING_DELAY_S = 5
 
 
 class NewTabPagePage(page_module.Page):
 
@@ skipping 16 matching lines @@
     # TODO(beaudoin): We have no guarantee the page has fully rendered and the
     #   JS has fully executed at that point. The right way to do it would be to
     #   toggle a Javascript variable in the page code and to wait for it here.
     #   This should be done when window.performance.mark is supported and we
     #   migrate to it instead of calling console.timeEnd here. If the test is
     #   failing flakily, we should use a better heuristic.
     action_runner.ExecuteJavaScript(
         "console.timeEnd('" + INTERACTION_NAME + "');")
 
 
-class NewTabPagePageSet(page_set_module.PageSet):
+class NewTabPagePageSet(story.StorySet):
   def __init__(self):
     super(NewTabPagePageSet, self).__init__(
         archive_data_file='data/new_tab_page_page.json',
-        bucket=page_set_module.PUBLIC_BUCKET)
+        cloud_storage_bucket=story.PUBLIC_BUCKET)
     self.AddUserStory(NewTabPagePage(page_set=self))