C++11 override style change for athena

athena/test/base/activity_lifetime_tracker.h

Index: athena/test/base/activity_lifetime_tracker.h
diff --git a/athena/test/base/activity_lifetime_tracker.h b/athena/test/base/activity_lifetime_tracker.h
index 670385f0a061fb4be2d510eb637fb33221b0c4ee..72426c9c488e443f96368d1a388feb5ce3954341 100644
--- a/athena/test/base/activity_lifetime_tracker.h
+++ b/athena/test/base/activity_lifetime_tracker.h
@@ -15,13 +15,13 @@ class Activity;
 class ActivityLifetimeTracker : public ActivityManagerObserver {
  public:
   ActivityLifetimeTracker();
-  virtual ~ActivityLifetimeTracker();
+  ~ActivityLifetimeTracker() override;
 
   // Called after an |activity| got created.
-  virtual void OnActivityStarted(Activity* activity) override;
+  void OnActivityStarted(Activity* activity) override;
 
   // Called before an |activity| gets destroyed.
-  virtual void OnActivityEnding(Activity* activity) override;
+  void OnActivityEnding(Activity* activity) override;
 
   // Returns the newly created activity (if any) and resets its reference.
   Activity* GetNewActivityAndReset();