Update perf page_set to use story_set

tools/perf/page_sets/tough_webgl_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 page_sets import webgl_supported_shared_state
+from telemetry import story
 from telemetry.page import page as page_module
-from telemetry.page import page_set as page_set_module
-
-from page_sets import webgl_supported_shared_state
 
 
 class ToughWebglCasesPage(page_module.Page):
 
   def __init__(self, url, page_set):
     super(ToughWebglCasesPage, self).__init__(
         url=url, page_set=page_set,
         shared_page_state_class=(
             webgl_supported_shared_state.WebGLSupportedSharedState),
         make_javascript_deterministic=False)
     self.archive_data_file = 'data/tough_webgl_cases.json'
 
 
   def RunNavigateSteps(self, action_runner):
     super(ToughWebglCasesPage, self).RunNavigateSteps(action_runner)
     action_runner.WaitForJavaScriptCondition(
         'document.readyState == "complete"')
     action_runner.Wait(2)
 
   def RunPageInteractions(self, action_runner):
     with action_runner.CreateInteraction('WebGLAnimation'):
       action_runner.Wait(5)
 
 
-class ToughWebglCasesPageSet(page_set_module.PageSet):
+class ToughWebglCasesPageSet(story.StorySet):
 
   """
   Description: Self-driven WebGL animation examples
   """
 
   def __init__(self):
     super(ToughWebglCasesPageSet, self).__init__(
       archive_data_file='data/tough_webgl_cases.json',
-      bucket=page_set_module.PUBLIC_BUCKET)
+      cloud_storage_bucket=story.PUBLIC_BUCKET)
 
     urls_list = [
       # pylint: disable=C0301
       'http://www.khronos.org/registry/webgl/sdk/demos/google/nvidia-vertex-buffer-object/index.html',
       # pylint: disable=C0301
       'http://www.khronos.org/registry/webgl/sdk/demos/google/san-angeles/index.html',
       # pylint: disable=C0301
       'http://www.khronos.org/registry/webgl/sdk/demos/google/particles/index.html',
       'http://www.khronos.org/registry/webgl/sdk/demos/webkit/Earth.html',
       # pylint: disable=C0301
       'http://www.khronos.org/registry/webgl/sdk/demos/webkit/ManyPlanetsDeep.html',
       'http://webglsamples.googlecode.com/hg/aquarium/aquarium.html',
       'http://webglsamples.googlecode.com/hg/blob/blob.html',
       # pylint: disable=C0301
       'http://webglsamples.googlecode.com/hg/dynamic-cubemap/dynamic-cubemap.html'
     ]
     for url in urls_list:
       self.AddUserStory(ToughWebglCasesPage(url, self))