Make credential_path a page attribute instead of page_set attribute.

tools/perf/page_sets/tough_scheduling_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.
 from telemetry.page import page as page_module
 from telemetry.page import page_set as page_set_module
 
 
 class ToughSchedulingCasesPage(page_module.Page):
 
   def __init__(self, url, page_set):
-    super(ToughSchedulingCasesPage, self).__init__(url=url, page_set=page_set)
-    self.credentials_path = 'data/credentials.json'
+    super(ToughSchedulingCasesPage, self).__init__(
+        url=url, page_set=page_set, credentials_path = 'data/credentials.json')
     self.user_agent_type = 'mobile'
     self.archive_data_file = 'data/tough_scheduling_cases.json'
 
   def RunSmoothness(self, action_runner):
     interaction = action_runner.BeginGestureInteraction(
         'ScrollAction', is_smooth=True)
     action_runner.ScrollPage()
     interaction.End()
 
 
@@ skipping 346 matching lines @@
     action_runner.ScrollBouncePage()
     interaction.End()
 
 
 class ToughSchedulingCasesPageSet(page_set_module.PageSet):
 
   """ Tough scheduler latency test cases """
 
   def __init__(self):
     super(ToughSchedulingCasesPageSet, self).__init__(
-        credentials_path='data/credentials.json',
         user_agent_type='mobile',
         archive_data_file='data/tough_scheduling_cases.json',
         bucket=page_set_module.INTERNAL_BUCKET)
 
     # Why: Simple scrolling baseline
     self.AddPage(ToughSchedulingCasesPage(
       'file://tough_scheduling_cases/simple_text_page.html',
       self))
     self.AddPage(Page1(self))
     self.AddPage(Page2(self))
@@ skipping 86 matching lines @@
       page_set=self))
     # Why: For measuring the latency of scroll-synchronized effects.
     self.AddPage(SynchronizedScrollOffsetPage(page_set=self))
     # Why: Good examples of poor initial scrolling
     self.AddPage(ToughSchedulingCasesPage(
       'http://www.latimes.com',
       self))
     self.AddPage(ToughSchedulingCasesPage(
       'http://m.espn.go.com/nhl/rankings',
        self))