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

base/synchronization/waitable_event.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_SYNCHRONIZATION_WAITABLE_EVENT_H_
 #define BASE_SYNCHRONIZATION_WAITABLE_EVENT_H_
 #pragma once
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
@@ skipping 127 matching lines @@
   // it doesn't crash. However, if we were to include the following members
   // directly then, on POSIX, one couldn't use WaitableEventWatcher to watch an
   // event which gets deleted. This mismatch has bitten us several times now,
   // so we have a kernel of the WaitableEvent, which is reference counted.
   // WaitableEventWatchers may then take a reference and thus match the Windows
   // behaviour.
   struct WaitableEventKernel :
       public RefCountedThreadSafe<WaitableEventKernel> {
    public:
     WaitableEventKernel(bool manual_reset, bool initially_signaled);
-    virtual ~WaitableEventKernel();
 
     bool Dequeue(Waiter* waiter, void* tag);
 
     base::Lock lock_;
     const bool manual_reset_;
     bool signaled_;
     std::list<Waiter*> waiters_;
+
+   private:
+    friend class RefCountedThreadSafe<WaitableEventKernel>;
+    ~WaitableEventKernel();
   };
 
   typedef std::pair<WaitableEvent*, size_t> WaiterAndIndex;
 
   // When dealing with arrays of WaitableEvent*, we want to sort by the address
   // of the WaitableEvent in order to have a globally consistent locking order.
   // In that case we keep them, in sorted order, in an array of pairs where the
   // second element is the index of the WaitableEvent in the original,
   // unsorted, array.
   static size_t EnqueueMany(WaiterAndIndex* waitables,
                             size_t count, Waiter* waiter);
 
   bool SignalAll();
   bool SignalOne();
   void Enqueue(Waiter* waiter);
 
   scoped_refptr<WaitableEventKernel> kernel_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(WaitableEvent);
 };
 
 }  // namespace base
 
 #endif  // BASE_SYNCHRONIZATION_WAITABLE_EVENT_H_