RefCounted types should not have public destructors

ipc/ipc_listener.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_LISTENER_H_
 #define IPC_IPC_LISTENER_H_
 
 #include "base/basictypes.h"
 #include "build/build_config.h"
 #include "ipc/ipc_export.h"
 
 namespace IPC {
 
 class Message;
 
 // Implemented by consumers of a Channel to receive messages.
 class IPC_EXPORT Listener {
  public:
-  virtual ~Listener() {}
-
   // Called when a message is received.  Returns true iff the message was
   // handled.
   virtual bool OnMessageReceived(const Message& message) = 0;
 
   // Called when the channel is connected and we have received the internal
   // Hello message from the peer.
   virtual void OnChannelConnected(int32 peer_pid) {}
 
   // Called when an error is detected that causes the channel to close.
   // This method is not called when a channel is closed normally.
   virtual void OnChannelError() {}
 
 #if defined(OS_POSIX)
   // Called on the server side when a channel that listens for connections
   // denies an attempt to connect.
   virtual void OnChannelDenied() {}
 
   // Called on the server side when a channel that listens for connections
   // has an error that causes the listening channel to close.
   virtual void OnChannelListenError() {}
 #endif  // OS_POSIX
+
+ protected:
+  virtual ~Listener() {}
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_LISTENER_H_