Kill PageSet.AddPage and its remaining usage

content/test/gpu/page_sets/memory_tests.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 MemoryTestsPage(page_module.Page):
 
   def __init__(self, page_set):
     super(MemoryTestsPage, self).__init__(
       url='file://../../data/gpu/mem_css3d.html', page_set=page_set,
       name='Memory.CSS3D')
     self.user_agent_type = 'desktop'
 
   def RunNavigateSteps(self, action_runner):
     action_runner.NavigateToPage(self)
     action_runner.WaitForJavaScriptCondition(
         'domAutomationController._finished', timeout_in_seconds=60)
 
 
 class MemoryTestsPageSet(page_set_module.PageSet):
 
   """ Tests that validate GPU memory management """
 
   def __init__(self):
     super(MemoryTestsPageSet, self).__init__(
       user_agent_type='desktop')
 
-    self.AddPage(MemoryTestsPage(self))
+    self.AddUserStory(MemoryTestsPage(self))