Revert of Attempting to resolve a race condition with PowerMonitor

content/browser/power_monitor_message_broadcaster.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 "content/browser/power_monitor_message_broadcaster.h"
 
 #include "base/power_monitor/power_monitor.h"
 #include "content/common/power_monitor_messages.h"
 #include "ipc/ipc_sender.h"
 
 namespace content {
 
 PowerMonitorMessageBroadcaster::PowerMonitorMessageBroadcaster(
     IPC::Sender* sender)
     : sender_(sender) {
-  base::PowerMonitor::AddObserver(this);
+  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
+  if (power_monitor)
+    power_monitor->AddObserver(this);
 }
 
 PowerMonitorMessageBroadcaster::~PowerMonitorMessageBroadcaster() {
-  base::PowerMonitor::RemoveObserver(this);
+  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
+  if (power_monitor)
+    power_monitor->RemoveObserver(this);
 }
 
 void PowerMonitorMessageBroadcaster::OnPowerStateChange(bool on_battery_power) {
   sender_->Send(new PowerMonitorMsg_PowerStateChange(on_battery_power));
 }
 
 void PowerMonitorMessageBroadcaster::OnSuspend() {
   sender_->Send(new PowerMonitorMsg_Suspend());
 }
 
 void PowerMonitorMessageBroadcaster::OnResume() {
   sender_->Send(new PowerMonitorMsg_Resume());
 }
 
 }  // namespace content