[system-health] Generalize loading stories to single-page stories

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.
+
+from page_sets.system_health import single_page_stories
+
+from telemetry import story
+
+
+class _MemorySystemHealthStorySet(story.StorySet):
+  """User stories for the System Health Plan.
+
+  See https://goo.gl/Jek2NL.
+  """
+  PLATFORM = NotImplemented
+
+  def __init__(self):
+    super(_MemorySystemHealthStorySet, self).__init__(
+        archive_data_file=('../data/memory_system_health_%s.json' %
+                           self.PLATFORM),
+        cloud_storage_bucket=story.PARTNER_BUCKET)
+    for story_class in single_page_stories.IterAllStoryClasses():
+      if self.PLATFORM not in story_class.SUPPORTED_PLATFORMS:
+        continue
+      self.AddStory(story_class(self))
+
+
+class DesktopMemorySystemHealthStorySet(_MemorySystemHealthStorySet):
+  """Desktop user stories for Chrome Memory System Health Plan."""
+  PLATFORM = 'desktop'
+
+
+class MobileMemorySystemHealthStorySet(_MemorySystemHealthStorySet):
+  """Mobile user stories for Chrome Memory System Health Plan."""
+  PLATFORM = 'mobile'