Virtual destructors should have virtual keyword.

chrome/test/test_notification_tracker.h

Index: chrome/test/test_notification_tracker.h
diff --git a/chrome/test/test_notification_tracker.h b/chrome/test/test_notification_tracker.h
index 7a9f947a0966d7dd2cd47b28ef0fd5f2acbf0f9a..21932c9d21e80f439e38a51fbab49eb2ac60f9c8 100644
--- a/chrome/test/test_notification_tracker.h
+++ b/chrome/test/test_notification_tracker.h
@@ -31,7 +31,7 @@ class TestNotificationTracker : public NotificationObserver {
   // ListenFor for the notifications you are interested in.
   TestNotificationTracker();
 
-  ~TestNotificationTracker();
+  virtual ~TestNotificationTracker();
 
   // Makes this object listen for the given notification with the given source.
   void ListenFor(NotificationType type, const NotificationSource& source);