Make credential_path a page attribute instead of page_set attribute.

tools/perf/page_sets/key_silk_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 KeySilkCasesPage(page_module.Page):
 
   def __init__(self, url, page_set):
-    super(KeySilkCasesPage, self).__init__(url=url, page_set=page_set)
-    self.credentials_path = 'data/credentials.json'
+    super(KeySilkCasesPage, self).__init__(
+        url=url, page_set=page_set, credentials_path = 'data/credentials.json')
     self.user_agent_type = 'mobile'
     self.archive_data_file = 'data/key_silk_cases.json'
 
   def RunNavigateSteps(self, action_runner):
     action_runner.NavigateToPage(self)
     action_runner.Wait(2)
 
   def RunSmoothness(self, action_runner):
     interaction = action_runner.BeginGestureInteraction(
         'ScrollAction', is_smooth=True)
@@ skipping 639 matching lines @@
     action_runner.Wait(10) # animation runs automatically
     interaction.End()
 
 
 class KeySilkCasesPageSet(page_set_module.PageSet):
 
   """ Pages hand-picked for project Silk. """
 
   def __init__(self):
     super(KeySilkCasesPageSet, self).__init__(
-      credentials_path='data/credentials.json',
       user_agent_type='mobile',
       archive_data_file='data/key_silk_cases.json',
       bucket=page_set_module.PARTNER_BUCKET)
 
     self.AddPage(Page1(self))
     self.AddPage(Page2(self))
     self.AddPage(Page3(self))
     self.AddPage(Page4(self))
     self.AddPage(Page5(self))
     self.AddPage(Page6(self))
@@ skipping 17 matching lines @@
     # Times out on Windows; crbug.com/338838
     # self.AddPage(Page22(self))
     self.AddPage(Page23(self))
     self.AddPage(Page24(self))
     self.AddPage(Page25(self))
     self.AddPage(Page26(self))
     self.AddPage(SVGIconRaster(self))
     self.AddPage(UpdateHistoryState(self))
     self.AddPage(TextSizeAnimation(self))
     self.AddPage(SilkFinance(self))