Update perf page_set to use story_set

tools/perf/page_sets/idle_multi_tab_cases.py

Index: tools/perf/page_sets/idle_multi_tab_cases.py
diff --git a/tools/perf/page_sets/idle_multi_tab_cases.py b/tools/perf/page_sets/idle_multi_tab_cases.py
index 30796abc460ebe8890126f9e9831ae1242ca7595..6911985868714511a29cfe45b2094bb456757992 100644
--- a/tools/perf/page_sets/idle_multi_tab_cases.py
+++ b/tools/perf/page_sets/idle_multi_tab_cases.py
@@ -4,11 +4,10 @@
 
 import os
 
-from telemetry.page import shared_page_state
-from telemetry.page import page_set as page_set_module
-
-from page_sets import top_pages
 from page_sets import top_7_stress
+from page_sets import top_pages
+from telemetry import story
+from telemetry.page import shared_page_state
 
 
 def _SpawnTab(action_runner):
@@ -47,14 +46,14 @@ def _CreateIdleMultiTabPageClass(base_page_cls, base_js):
   return DerivedIdleMultiTabPage
 
 
-class IdleMultiTabCasesPageSet(page_set_module.PageSet):
+class IdleMultiTabCasesPageSet(story.StorySet):
 
   """ Pages for testing GC efficiency on idle pages. """
 
   def __init__(self):
     super(IdleMultiTabCasesPageSet, self).__init__(
         archive_data_file='data/top_25.json',
-        bucket=page_set_module.PARTNER_BUCKET)
+        cloud_storage_bucket=story.PARTNER_BUCKET)
     with open(os.path.join(os.path.dirname(__file__),
               'idle_multi_tab_cases.js')) as f:
       base_js = f.read()