Update perf page_set to use story_set

tools/perf/page_sets/webrtc_cases.py

 # 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.
 import os
 
+from telemetry import story
 from telemetry.page import page as page_module
-from telemetry.page import page_set as page_set_module
-
 
 WEBRTC_GITHUB_SAMPLES_URL = 'http://webrtc.github.io/samples/src/content/'
 
 
 class WebrtcCasesPage(page_module.Page):
 
   def __init__(self, url, page_set, name):
     super(WebrtcCasesPage, self).__init__(
         url=url, page_set=page_set, name=name)
 
@@ skipping 144 matching lines @@
         page_set=page_set)
 
   def RunPageInteractions(self, action_runner):
     # It won't have time to finish the 512 MB, but we're only interested in
     # cpu + memory anyway rather than how much data we manage to transfer.
     action_runner.ExecuteJavaScript('megsToSend.value = 512;')
     action_runner.ClickElement('button[id="sendTheData"]')
     action_runner.Wait(30)
 
 
-class WebrtcCasesPageSet(page_set_module.PageSet):
+class WebrtcCasesPageSet(story.StorySet):
 
   """ WebRTC tests for Real-time audio and video communication. """
 
   def __init__(self):
     super(WebrtcCasesPageSet, self).__init__(
       archive_data_file='data/webrtc_cases.json',
-      bucket=page_set_module.PUBLIC_BUCKET)
+      cloud_storage_bucket=story.PUBLIC_BUCKET)
 
     self.AddUserStory(Page1(self))
     self.AddUserStory(Page2(self))
     self.AddUserStory(Page3(self))
     # Disable page 4-7 until we can implement http://crbug.com/468732. We can
     # get data out from the tests, but it's not very useful yet.
     self.AddUserStory(Page8(self))
     self.AddUserStory(Page9(self))