Add OVERRIDE to content/.

content/test/test_notification_tracker.h

Index: content/test/test_notification_tracker.h
diff --git a/content/test/test_notification_tracker.h b/content/test/test_notification_tracker.h
index 16b91c2e419a3135c6b2ef7c72563840d3a80e1a..ef1d7cec657da9e3d45894287e4143cd9fc99cf4 100644
--- a/content/test/test_notification_tracker.h
+++ b/content/test/test_notification_tracker.h
@@ -8,6 +8,7 @@
 
 #include <vector>
 
+#include "base/compiler_specific.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
@@ -69,7 +70,7 @@ class TestNotificationTracker : public content::NotificationObserver {
  protected:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
-                       const content::NotificationDetails& details);
+                       const content::NotificationDetails& details) OVERRIDE;
  private:
   content::NotificationRegistrar registrar_;