Update perf page_set to use story_set

tools/perf/page_sets/tough_webgl_cases.py

Index: tools/perf/page_sets/tough_webgl_cases.py
diff --git a/tools/perf/page_sets/tough_webgl_cases.py b/tools/perf/page_sets/tough_webgl_cases.py
index 843f9b24d91a97cfc95bd50f54f607560e2f1ea3..e2bbe76460776569ef858f967be2af2820b9336b 100644
--- a/tools/perf/page_sets/tough_webgl_cases.py
+++ b/tools/perf/page_sets/tough_webgl_cases.py
@@ -2,10 +2,9 @@
 # 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
-
 from page_sets import webgl_supported_shared_state
+from telemetry import story
+from telemetry.page import page as page_module
 
 
 class ToughWebglCasesPage(page_module.Page):
@@ -30,7 +29,7 @@ class ToughWebglCasesPage(page_module.Page):
       action_runner.Wait(5)
 
 
-class ToughWebglCasesPageSet(page_set_module.PageSet):
+class ToughWebglCasesPageSet(story.StorySet):
 
   """
   Description: Self-driven WebGL animation examples
@@ -39,7 +38,7 @@ class ToughWebglCasesPageSet(page_set_module.PageSet):
   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