Add virtual to some base classes that have virtual methods...

base/message_loop_proxy.h

 // Copyright (c) 2010 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_PROXY_H_
 #define BASE_MESSAGE_LOOP_PROXY_H_
 
 #include "base/basictypes.h"
 #include "base/ref_counted.h"
 #include "base/task.h"
@@ skipping 37 matching lines @@
                    T* object) {
     return PostNonNestableTask(from_here, new ReleaseTask<T>(object));
   }
 
   // Factory method for creating an implementation of MessageLoopProxy
   // for the current thread.
   static scoped_refptr<MessageLoopProxy> CreateForCurrentThread();
 
  protected:
   friend struct MessageLoopProxyTraits;
+
+  virtual ~MessageLoopProxy() { }
+
   // Called when the proxy is about to be deleted. Subclasses can override this
   // to provide deletion on specific threads.
   virtual void OnDestruct() {
     delete this;
   }
 };
 
 struct MessageLoopProxyTraits {
   static void Destruct(MessageLoopProxy* proxy) {
     proxy->OnDestruct();
   }
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_PROXY_H_