Virtual destructors should have virtual keyword.

base/message_loop.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_H_
 #pragma once
 
 #include <queue>
 #include <string>
@@ skipping 93 matching lines @@
   //
   enum Type {
     TYPE_DEFAULT,
     TYPE_UI,
     TYPE_IO
   };
 
   // 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();
 
   static void EnableHistogrammer(bool enable_histogrammer);
 
   // A DestructionObserver is notified when the current MessageLoop is being
   // destroyed.  These obsevers are notified prior to MessageLoop::current()
   // being changed to return NULL.  This gives interested parties the chance to
   // do final cleanup that depends on the MessageLoop.
@@ skipping 565 matching lines @@
 #endif  // defined(OS_POSIX)
 };
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 COMPILE_ASSERT(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
                MessageLoopForIO_should_not_have_extra_member_variables);
 
 #endif  // BASE_MESSAGE_LOOP_H_