Add loading mobile story set

tools/perf/page_sets/page_cycler_story.py

 # Copyright 2016 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 page
 from telemetry.page import cache_temperature as cache_temperature_module
 from telemetry.page import shared_page_state
 
 _TTI_WAIT_TIME = 10
 
 class PageCyclerStory(page.Page):
 
-  def __init__(self, url, page_set,
+  def __init__(self, url, page_set, labels=None,
       shared_page_state_class=shared_page_state.SharedDesktopPageState,
       cache_temperature=cache_temperature_module.ANY, **kwargs):
     super(PageCyclerStory, self).__init__(
-        url=url, page_set=page_set,
+        url=url, page_set=page_set, labels=labels,
         shared_page_state_class=shared_page_state_class,
         cache_temperature=cache_temperature,
         **kwargs)
 
   def RunPageInteractions(self, action_runner):
     action_runner.tab.WaitForDocumentReadyStateToBeComplete()
     action_runner.Wait(_TTI_WAIT_TIME)