[Telemetry] Add benchmark that doesn't launch chrome and collects platform data.

tools/perf/page_sets/idle_platform.py

+# Copyright 2017 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 time
+
+from telemetry.page import shared_page_state
+from telemetry import story
+
+
+class _IdleSharedState(shared_page_state.SharedPageState):
+  def __init__(self, test, finder_options, story_set):
+    super(_IdleSharedState, self).__init__(test, finder_options, story_set)
+    self._current_story = None
+
+  def WillRunStory(self, current_story):
+    self._current_story = current_story
+    assert self.platform.tracing_controller.is_tracing_running
+
+  def RunStory(self, _):
+    self._current_story.Run(self)
+
+  def DidRunStory(self, _):
+    self._current_story = None
+
+
+class _IdleStory(story.Story):
+  def __init__(self, name, duration):
+    super(_IdleStory, self).__init__(
+        shared_state_class=_IdleSharedState, name=name)
+    self._duration = duration
+
+  def Run(self, shared_state):
+    time.sleep(self._duration)
+
+
+class IdleStorySet(story.StorySet):
+  def __init__(self):
+    super(IdleStorySet, self).__init__()
+    self.AddStory(_IdleStory('IdleStory_10s', 10))
+    self.AddStory(_IdleStory('IdleStory_60s', 60))
+    self.AddStory(_IdleStory('IdleStory_120s', 120))