Virtual destructors should have virtual keyword.

base/message_loop.h

Index: base/message_loop.h
diff --git a/base/message_loop.h b/base/message_loop.h
index c660c9ead863c14b3aa2558f79809542dd4f2a5b..9a03d6b5a53d345a64d79214ff4509d11ec0c3bd 100644
--- a/base/message_loop.h
+++ b/base/message_loop.h
@@ -111,7 +111,7 @@ class BASE_API MessageLoop : public base::MessagePump::Delegate {
   // Normally, it is not necessary to instantiate a MessageLoop.  Instead, it
   // is typical to make use of the current thread's MessageLoop instance.
   explicit MessageLoop(Type type = TYPE_DEFAULT);
-  ~MessageLoop();
+  virtual ~MessageLoop();
 
   // Returns the MessageLoop object for the current thread, or null if none.
   static MessageLoop* current();