Revert of Attempting to resolve a race condition with PowerMonitor

base/timer/hi_res_timer_manager_win.cc

Index: base/timer/hi_res_timer_manager_win.cc
diff --git a/base/timer/hi_res_timer_manager_win.cc b/base/timer/hi_res_timer_manager_win.cc
index 98b41d700926c76cf6849c21d3add8adc299b1e8..692f72b4e594481897bf022e256d51bb65b1f1b9 100644
--- a/base/timer/hi_res_timer_manager_win.cc
+++ b/base/timer/hi_res_timer_manager_win.cc
@@ -11,12 +11,14 @@
 
 HighResolutionTimerManager::HighResolutionTimerManager()
     : hi_res_clock_available_(false) {
-  base::PowerMonitor::AddObserver(this);
-  UseHiResClock(!base::PowerMonitor::IsOnBatteryPower());
+  base::PowerMonitor* power_monitor = base::PowerMonitor::Get();
+  DCHECK(power_monitor != NULL);
+  power_monitor->AddObserver(this);
+  UseHiResClock(!power_monitor->IsOnBatteryPower());
 }
 
 HighResolutionTimerManager::~HighResolutionTimerManager() {
-  base::PowerMonitor::RemoveObserver(this);
+  base::PowerMonitor::Get()->RemoveObserver(this);
   UseHiResClock(false);
 }