Make credential_path a page attribute instead of page_set attribute.

tools/perf/page_sets/top_25.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
 
 
 def _GetCurrentLocation(action_runner):
   return action_runner.EvaluateJavaScript('document.location.href')
 
 
 def _WaitForLocationChange(action_runner, old_href):
   action_runner.WaitForJavaScriptCondition(
       'document.location.href != "%s"' % old_href)
 
 
 class Top25Page(page_module.Page):
 
   def __init__(self, url, page_set, name=''):
-    super(Top25Page, self).__init__(url=url, page_set=page_set, name=name)
-    self.credentials_path = 'data/credentials.json'
+    super(Top25Page, self).__init__(
+        url=url, page_set=page_set, name=name,
+        credentials_path='data/credentials.json')
     self.user_agent_type = 'desktop'
     self.archive_data_file = 'data/top_25.json'
 
   def RunSmoothness(self, action_runner):
     interaction = action_runner.BeginGestureInteraction(
         'ScrollAction', is_smooth=True)
     action_runner.ScrollPage()
     interaction.End()
 
   def RunRepaint(self, action_runner):
@@ skipping 483 matching lines @@
     action_runner.NavigateToPage(self)
     action_runner.Wait(2)
 
 
 class Top25PageSet(page_set_module.PageSet):
 
   """ Pages hand-picked for 2012 CrOS scrolling tuning efforts. """
 
   def __init__(self):
     super(Top25PageSet, self).__init__(
-      credentials_path='data/credentials.json',
       user_agent_type='desktop',
       archive_data_file='data/top_25.json',
       bucket=page_set_module.PARTNER_BUCKET)
 
     self.AddPage(GoogleWebSearchPage(self))
     self.AddPage(GmailPage(self))
     self.AddPage(GoogleCalendarPage(self))
     self.AddPage(GoogleImageSearchPage(self))
     self.AddPage(GoogleDocPage(self))
     self.AddPage(GooglePlusPage(self))
@@ skipping 24 matching lines @@
       # Why: #1 Alexa reference
       'http://answers.yahoo.com',
       # Why: #1 Alexa sports
       'http://sports.yahoo.com/',
       # Why: top tech blog
       'http://techcrunch.com'
     ]
 
     for url in other_urls:
       self.AddPage(Top25Page(url, self))