Attempting to resolve a race condition with PowerMonitor

content/gpu/gpu_watchdog_thread.cc

Index: content/gpu/gpu_watchdog_thread.cc
diff --git a/content/gpu/gpu_watchdog_thread.cc b/content/gpu/gpu_watchdog_thread.cc
index 940d07e72ac43ae0cb6f36e1b160ab48c6bd7f24..ff2d2ad447deb3fc8119ad17e82b37336c8aaa07 100644
--- a/content/gpu/gpu_watchdog_thread.cc
+++ b/content/gpu/gpu_watchdog_thread.cc
@@ -114,9 +114,7 @@ GpuWatchdogThread::~GpuWatchdogThread() {
   CloseHandle(watched_thread_handle_);
 #endif
 
-  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
-  if (power_monitor)
-    power_monitor->RemoveObserver(this);
+  base::PowerMonitor::RemoveObserverThreadSafe(this);
 
 #if defined(OS_CHROMEOS)
   if (tty_file_)
@@ -266,9 +264,7 @@ void GpuWatchdogThread::AddPowerObserver() {
 }
 
 void GpuWatchdogThread::OnAddPowerObserver() {
-  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
-  DCHECK(power_monitor);
-  power_monitor->AddObserver(this);
+  DCHECK(base::PowerMonitor::AddObserverThreadSafe(this));
 }
 
 void GpuWatchdogThread::OnSuspend() {