Standardize usage of virtual/override/final in content/

content/child/power_monitor_broadcast_source.h

Index: content/child/power_monitor_broadcast_source.h
diff --git a/content/child/power_monitor_broadcast_source.h b/content/child/power_monitor_broadcast_source.h
index 42d3e0ca88cff3ce50a9be718bc8009b643518fc..b0d34162fbb4e09baf93dcb8cd97f2337a01d7ca 100644
--- a/content/child/power_monitor_broadcast_source.h
+++ b/content/child/power_monitor_broadcast_source.h
@@ -23,14 +23,14 @@ class CONTENT_EXPORT PowerMonitorBroadcastSource :
     public base::PowerMonitorSource {
  public:
   explicit PowerMonitorBroadcastSource();
-  virtual ~PowerMonitorBroadcastSource();
+  ~PowerMonitorBroadcastSource() override;
 
   IPC::MessageFilter* GetMessageFilter();
 
  private:
   friend class PowerMessageFilter;
 
-  virtual bool IsOnBatteryPowerImpl() override;
+  bool IsOnBatteryPowerImpl() override;
 
   void OnPowerStateChange(bool on_battery_power);
   void OnSuspend();