RefCounted types should not have public destructors

ipc/ipc_sender.h

 // Copyright (c) 2012 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 IPC_IPC_SENDER_H_
 #define IPC_IPC_SENDER_H_
 
 #include "ipc/ipc_export.h"
 
 namespace IPC {
 
 class Message;
 
 class IPC_EXPORT Sender {
  public:
-  virtual ~Sender() {}
-
   // Sends the given IPC message.  The implementor takes ownership of the
   // given Message regardless of whether or not this method succeeds.  This
   // is done to make this method easier to use.  Returns true on success and
   // false otherwise.
   virtual bool Send(Message* msg) = 0;
+
+ protected:
+  virtual ~Sender() {}
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SENDER_H_