[scheduler]: Avoid waking up the scheduler to end long idle periods.

components/scheduler/scheduler.gypi

 # Copyright 2015 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.
 
 {
   'variables': {
     'scheduler_common_sources': [
       'common/scheduler_switches.cc',
       'common/scheduler_switches.h',
     ],
     'scheduler_sources': [
       'child/cancelable_closure_holder.cc',
       'child/cancelable_closure_holder.h',
       'child/child_scheduler.h',
       'child/idle_helper.cc',
       'child/idle_helper.h',
       'child/nestable_single_thread_task_runner.h',
       'child/null_idle_task_runner.cc',
       'child/null_idle_task_runner.h',
       'child/null_worker_scheduler.cc',
       'child/null_worker_scheduler.h',
+      'child/pollable_thread_safe_flag.cc',
+      'child/pollable_thread_safe_flag.h',
       'child/prioritizing_task_queue_selector.cc',
       'child/prioritizing_task_queue_selector.h',
       'child/scheduler_helper.cc',
       'child/scheduler_helper.h',
       'child/scheduler_message_loop_delegate.cc',
       'child/scheduler_message_loop_delegate.h',
       'child/single_thread_idle_task_runner.cc',
       'child/single_thread_idle_task_runner.h',
       'child/task_queue_manager.cc',
       'child/task_queue_manager.h',
@@ skipping 19 matching lines @@
       'renderer/renderer_scheduler_impl.cc',
       'renderer/renderer_scheduler_impl.h',
       'renderer/renderer_web_scheduler_impl.cc',
       'renderer/renderer_web_scheduler_impl.h',
       'renderer/webthread_impl_for_renderer_scheduler.cc',
       'renderer/webthread_impl_for_renderer_scheduler.h',
       'scheduler_export.h',
     ],
   },
 }