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

tools/perf/page_sets/idle_platform.py

+# Copyright 2014 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, idle_time=30):

[rnephew (Reviews Here), 2017/03/13 21:29:18]

I keep flopping between thinking this should be here or in IdlePlatformPage().
Any strong opinions on this?

[nednguyen, 2017/03/13 21:35:51]

shared_state is construct by story_runner, so its constructor's signature must
be exactly the same as
https://github.com/catapult-project/catapult/blob/master/telemetry/telemetry/...

+    super(_IdleSharedState, self).__init__(test, finder_options, story_set)
+    self._current_story = None
+    self._idle_time = idle_time
+
+  def WillRunStory(self, current_story):
+    self._current_story = current_story
+    if not self.platform.tracing_controller.is_tracing_running:
+      # For TimelineBasedMeasurement benchmarks, tracing has already started.
+      # For PageTest benchmarks, tracing has not yet started. We need to make
+      # sure no tracing state is left before starting the browser for PageTest
+      # benchmarks.
+      self.platform.tracing_controller.ClearStateIfNeeded()
+
+  def RunStory(self, _):
+    self._current_story.Run(self)
+
+  def DidRunStory(self, _):
+    self._current_story = None
+
+  @property
+  def idle_time(self):
+    return self._idle_time
+
+
+class IdlePlatformPage(story.Story):
+  def __init__(self, name):
+    super(IdlePlatformPage, self).__init__(
+        shared_state_class=_IdleSharedState, name=name)
+
+  def Run(self, shared_state):
+    time.sleep(shared_state.idle_time)
+
+
+class IdlePlatformPageSet(story.StorySet):
+  def __init__(self):
+    super(IdlePlatformPageSet, self).__init__(
+        archive_data_file=None,
+        cloud_storage_bucket=story.PARTNER_BUCKET)
+    self.AddStory(IdlePlatformPage('Idle Platform'))