Allow PowerMonitorDeviceSource to be used from sequenced tasks.

base/power_monitor/power_monitor_device_source.cc

 // Copyright 2013 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.
 
 #include "base/power_monitor/power_monitor_device_source.h"
 
-#include "base/threading/thread_task_runner_handle.h"
-
 namespace base {
 
 PowerMonitorDeviceSource::PowerMonitorDeviceSource() {
-  DCHECK(ThreadTaskRunnerHandle::IsSet());
-
 #if defined(OS_MACOSX)
   PlatformInit();
 #endif
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
   // Provide the correct battery status if possible. Others platforms, such as
   // Android and ChromeOS, will update their status once their backends are
   // actually initialized.
   SetInitialOnBatteryPowerState(IsOnBatteryPowerImpl());
 #endif
 }
 
 PowerMonitorDeviceSource::~PowerMonitorDeviceSource() {
 #if defined(OS_MACOSX)
   PlatformDestroy();
 #endif
 }
 
 }  // namespace base