Standardize usage of virtual/override/final in mojo/

mojo/edk/system/simple_dispatcher.h

Index: mojo/edk/system/simple_dispatcher.h
diff --git a/mojo/edk/system/simple_dispatcher.h b/mojo/edk/system/simple_dispatcher.h
index 400e3020e13f973fd9d345e2c36a5530f6ea4e19..b1260ef2bcd248d1e5cce6bc110d7a56500337c5 100644
--- a/mojo/edk/system/simple_dispatcher.h
+++ b/mojo/edk/system/simple_dispatcher.h
@@ -22,7 +22,7 @@ namespace system {
 class MOJO_SYSTEM_IMPL_EXPORT SimpleDispatcher : public Dispatcher {
  protected:
   SimpleDispatcher();
-  virtual ~SimpleDispatcher();
+  ~SimpleDispatcher() override;
 
   // To be called by subclasses when the state changes (so
   // |GetHandleSignalsStateImplNoLock()| should be checked again). Must be
@@ -30,15 +30,13 @@ class MOJO_SYSTEM_IMPL_EXPORT SimpleDispatcher : public Dispatcher {
   void HandleSignalsStateChangedNoLock();
 
   // |Dispatcher| protected methods:
-  virtual void CancelAllWaitersNoLock() override;
-  virtual MojoResult AddWaiterImplNoLock(
-      Waiter* waiter,
-      MojoHandleSignals signals,
-      uint32_t context,
-      HandleSignalsState* signals_state) override;
-  virtual void RemoveWaiterImplNoLock(
-      Waiter* waiter,
-      HandleSignalsState* signals_state) override;
+  void CancelAllWaitersNoLock() override;
+  MojoResult AddWaiterImplNoLock(Waiter* waiter,
+                                 MojoHandleSignals signals,
+                                 uint32_t context,
+                                 HandleSignalsState* signals_state) override;
+  void RemoveWaiterImplNoLock(Waiter* waiter,
+                              HandleSignalsState* signals_state) override;
 
  private:
   // Protected by |lock()|: