Objects that derive from RefCounted/RefCountedThreadSafe should not have public dtors.

remoting/base/plugin_message_loop_proxy.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 REMOTING_BASE_PLUGIN_MESSAGE_LOOP_H_
 #define REMOTING_BASE_PLUGIN_MESSAGE_LOOP_H_
 
 #include "base/callback_forward.h"
 #include "base/compiler_specific.h"
 #include "base/message_loop_proxy.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/platform_thread.h"
 
 namespace remoting {
 
 // MessageLoopProxy for plugin main threads.
 class PluginMessageLoopProxy : public base::MessageLoopProxy {
  public:
   class Delegate {
    public:
     Delegate() { }
     virtual ~Delegate() { }
 
     virtual bool RunOnPluginThread(
         base::TimeDelta delay, void(function)(void*), void* data) = 0;
   };
 
   // Caller keeps ownership of delegate.
   PluginMessageLoopProxy(Delegate* delegate);
-  virtual ~PluginMessageLoopProxy();
 
   void Detach();
 
   // base::MessageLoopProxy implementation.
   virtual bool PostDelayedTask(
       const tracked_objects::Location& from_here,
       const base::Closure& task,
       int64 delay_ms) OVERRIDE;
   virtual bool PostDelayedTask(
       const tracked_objects::Location& from_here,
       const base::Closure& task,
       base::TimeDelta delay) OVERRIDE;
   virtual bool PostNonNestableDelayedTask(
       const tracked_objects::Location& from_here,
       const base::Closure& task,
       int64 delay_ms) OVERRIDE;
   virtual bool PostNonNestableDelayedTask(
       const tracked_objects::Location& from_here,
       const base::Closure& task,
       base::TimeDelta delay) OVERRIDE;
 
   virtual bool RunsTasksOnCurrentThread() const OVERRIDE;
 
+ protected:
+  virtual ~PluginMessageLoopProxy();
+
  private:
   static void TaskSpringboard(void* data);
 
   void RunClosureIf(const base::Closure& task);
 
   base::PlatformThreadId plugin_thread_id_;
 
   // |lock_| must be acquired when accessing |delegate_|.
   base::Lock lock_;
   Delegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginMessageLoopProxy);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_BASE_PLUGIN_MESSAGE_LOOP_H_