Migrate from telemetry PageSet -> StorySet.

tools/chrome_proxy/integration_tests/chrome_proxy_pagesets/__init__.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.
 
 import inspect
 import os
 import sys
 
 from telemetry.core import discover
-from telemetry.page import page_set
+from telemetry import story
 import video
 
 
-# Import all submodules' PageSet classes.
+# Import all submodules' StorySet classes.
 start_dir = os.path.dirname(os.path.abspath(__file__))
 top_level_dir = os.path.abspath(os.path.join(start_dir, os.pardir, os.pardir))
-base_class = page_set.PageSet
+base_class = story.StorySet
 for cls in discover.DiscoverClasses(
     start_dir, top_level_dir, base_class).values():
   setattr(sys.modules[__name__], cls.__name__, cls)
 
 # DiscoverClasses makes the assumption that there is exactly one matching
 # class per file, however the following are declared in the same file.
-for cls in (video.VideoDirectPageSet,
-            video.VideoProxiedPageSet,
-            video.VideoComparePageSet):
+for cls in (video.VideoDirectStorySet,
+            video.VideoProxiedStorySet,
+            video.VideoCompareStorySet):
   setattr(sys.modules[__name__], cls.__name__, cls)