Update {virtual,override} to follow C++11 style in device.

device/battery/battery_status_manager_win.cc

Index: device/battery/battery_status_manager_win.cc
diff --git a/device/battery/battery_status_manager_win.cc b/device/battery/battery_status_manager_win.cc
index 6ad13da8a4b6e68c2711d6271d69eb4ba622a4eb..50ceac758bde4f063585edeb997e7ecc989825c0 100644
--- a/device/battery/battery_status_manager_win.cc
+++ b/device/battery/battery_status_manager_win.cc
@@ -160,18 +160,16 @@ class BatteryStatusManagerWin : public BatteryStatusManager {
  public:
   explicit BatteryStatusManagerWin(const BatteryCallback& callback)
       : battery_observer_(new BatteryStatusObserver(callback)) {}
-  virtual ~BatteryStatusManagerWin() { battery_observer_->Stop(); }
+  ~BatteryStatusManagerWin() override { battery_observer_->Stop(); }
 
  public:
   // BatteryStatusManager:
-  virtual bool StartListeningBatteryChange() override {
+  bool StartListeningBatteryChange() override {
     battery_observer_->Start();
     return true;
   }
 
-  virtual void StopListeningBatteryChange() override {
-    battery_observer_->Stop();
-  }
+  void StopListeningBatteryChange() override { battery_observer_->Stop(); }
 
  private:
   scoped_ptr<BatteryStatusObserver> battery_observer_;