RefCounted types should not have public destructors

ppapi/proxy/var_serialization_rules.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 PPAPI_PROXY_VAR_SERIALIZATION_RULES_H_
 #define PPAPI_PROXY_VAR_SERIALIZATION_RULES_H_
 
 #include "base/memory/ref_counted.h"
 #include "ppapi/c/pp_var.h"
 
 #include <string>
 
 namespace ppapi {
 namespace proxy {
 
 // Encapsulates the rules for serializing and deserializing vars to and from
 // the local process. The renderer and the plugin process each have separate
 // bookkeeping rules.
 class VarSerializationRules : public base::RefCounted<VarSerializationRules> {
  public:
-  virtual ~VarSerializationRules() {}
-
   // Caller-owned calls --------------------------------------------------------
   //
   // A caller-owned call is when doing a function call with a "normal" input
   // argument. The caller has a reference to the var, and the caller is
   // responsible for freeing that reference.
 
   // Prepares the given var for sending to the remote process. For object vars,
   // the returned var will contain the id valid for the host process.
   // Otherwise, the returned var is valid in the local process.
   virtual PP_Var SendCallerOwned(const PP_Var& var) = 0;
@@ skipping 39 matching lines @@
   // local process. This same var must be passed to EndSendPassRef.
   virtual PP_Var BeginSendPassRef(const PP_Var& var) = 0;
   virtual void EndSendPassRef(const PP_Var& var) = 0;
 
   // ---------------------------------------------------------------------------
 
   virtual void ReleaseObjectRef(const PP_Var& var) = 0;
 
  protected:
   VarSerializationRules() {}
+  virtual ~VarSerializationRules() {}
+
+ private:
+  friend class base::RefCounted<VarSerializationRules>;
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_VAR_SERIALIZATION_RULES_H_