Revert of Attempting to resolve a race condition with PowerMonitor

content/browser/power_monitor_message_broadcaster.cc

Index: content/browser/power_monitor_message_broadcaster.cc
diff --git a/content/browser/power_monitor_message_broadcaster.cc b/content/browser/power_monitor_message_broadcaster.cc
index 82affddbdba85691cec0fcc02b2921766fdbda1c..23de161b05c7225af72b1efb3dcd45c8545c879f 100644
--- a/content/browser/power_monitor_message_broadcaster.cc
+++ b/content/browser/power_monitor_message_broadcaster.cc
@@ -13,11 +13,15 @@
 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) {