Standardize usage of virtual/override/final in base/

base/message_loop/message_pump_default.h

Index: base/message_loop/message_pump_default.h
diff --git a/base/message_loop/message_pump_default.h b/base/message_loop/message_pump_default.h
index e9f73028dc06e9482fcb2a1d668ffe1b164891e4..d63e8101a933b0a3494f746fe76e90e218d4748d 100644
--- a/base/message_loop/message_pump_default.h
+++ b/base/message_loop/message_pump_default.h
@@ -15,13 +15,13 @@ namespace base {
 class BASE_EXPORT MessagePumpDefault : public MessagePump {
  public:
   MessagePumpDefault();
-  virtual ~MessagePumpDefault();
+  ~MessagePumpDefault() override;
 
   // MessagePump methods:
-  virtual void Run(Delegate* delegate) override;
-  virtual void Quit() override;
-  virtual void ScheduleWork() override;
-  virtual void ScheduleDelayedWork(const TimeTicks& delayed_work_time) override;
+  void Run(Delegate* delegate) override;
+  void Quit() override;
+  void ScheduleWork() override;
+  void ScheduleDelayedWork(const TimeTicks& delayed_work_time) override;
 
  private:
   // This flag is set to false when Run should return.