[system-health] Add support for recording stories directly through story set

tools/perf/page_sets/system_health/system_health_stories.py

 # Copyright 2016 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 os
 
 from page_sets.system_health import platforms
 from page_sets.system_health import system_health_story
 
 from telemetry import story
@@ skipping 13 matching lines @@
     assert platform in platforms.ALL_PLATFORMS
 
     for story_class in _IterAllSystemHealthStoryClasses():
       if (story_class.ABSTRACT_STORY or
           platform not in story_class.SUPPORTED_PLATFORMS or
           case and not story_class.NAME.startswith(case + ':')):
         continue
       self.AddStory(story_class(self, take_memory_measurement))
 
 
+class DesktopSystemHealthStorySet(SystemHealthStorySet):
+  """Desktop user stories for the System Health Plan.
+
+  Note: This story set is only intended to be used for recording stories via
+  tools/perf/record_wpr. If you would like to use it in a benchmark, please use
+  the generic SystemHealthStorySet class instead (you'll need to override the
+  CreateStorySet method of your benchmark).
+  """
+  def __init__(self):
+    super(DesktopSystemHealthStorySet, self).__init__(
+        'desktop', take_memory_measurement=False)
+
+
+class MobileSystemHealthStorySet(SystemHealthStorySet):
+  """Mobile user stories for the System Health Plan.
+
+  Note: This story set is only intended to be used for recording stories via
+  tools/perf/record_wpr. If you would like to use it in a benchmark, please use
+  the generic SystemHealthStorySet class instead (you'll need to override the
+  CreateStorySet method of your benchmark).
+  """
+  def __init__(self):
+    super(MobileSystemHealthStorySet, self).__init__(
+        'mobile', take_memory_measurement=False)
+
+
 def _IterAllSystemHealthStoryClasses():
   start_dir = os.path.dirname(os.path.abspath(__file__))
   # Sort the classes by their names so that their order is stable and
   # deterministic.
   for unused_cls_name, cls in sorted(discover.DiscoverClasses(
       start_dir=start_dir,
       top_level_dir=os.path.dirname(start_dir),
       base_class=system_health_story.SystemHealthStory).iteritems()):
     yield cls