RefCounted types should not have public destructors, net/ edition

net/base/network_change_notifier.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 NET_BASE_NETWORK_CHANGE_NOTIFIER_H_
 #define NET_BASE_NETWORK_CHANGE_NOTIFIER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/observer_list_threadsafe.h"
@@ skipping 22 matching lines @@
     // The HOSTS file has changed.
     CHANGE_DNS_HOSTS = 1 << 1,
     // The watcher has started.
     CHANGE_DNS_WATCH_STARTED = 1 << 2,
     // The watcher has failed and will not be available until further notice.
     CHANGE_DNS_WATCH_FAILED = 1 << 3,
   };
 
   class NET_EXPORT IPAddressObserver {
    public:
-    virtual ~IPAddressObserver() {}
-
     // Will be called when the IP address of the primary interface changes.
     // This includes when the primary interface itself changes.
     virtual void OnIPAddressChanged() = 0;
 
    protected:
     IPAddressObserver() {}
+    virtual ~IPAddressObserver() {}
 
    private:
     DISALLOW_COPY_AND_ASSIGN(IPAddressObserver);
   };
 
   class NET_EXPORT OnlineStateObserver {
    public:
-    virtual ~OnlineStateObserver() {}
-
     // Will be called when the online state of the system may have changed.
     // See NetworkChangeNotifier::IsOffline() for important caveats about
     // the unreliability of this signal.
     virtual void OnOnlineStateChanged(bool online) = 0;
 
    protected:
     OnlineStateObserver() {}
+    virtual ~OnlineStateObserver() {}

[willchan no longer on Chromium, 2012/05/21 14:31:08]

These types aren't refcounted, why are their destructors being made protected?

 
    private:
     DISALLOW_COPY_AND_ASSIGN(OnlineStateObserver);
   };
 
   class NET_EXPORT DNSObserver {
    public:
-    virtual ~DNSObserver() {}
-
     // Will be called when the DNS settings of the system may have changed.
     // The flags set in |detail| provide the specific set of changes.
     virtual void OnDNSChanged(unsigned detail) = 0;
 
    protected:
     DNSObserver() {}
+    virtual ~DNSObserver() {}
 
    private:
     DISALLOW_COPY_AND_ASSIGN(DNSObserver);
   };
 
   virtual ~NetworkChangeNotifier();
 
   // See the description of NetworkChangeNotifier::IsOffline().
   // Implementations must be thread-safe. Implementations must also be
   // cheap as this could be called (repeatedly) from the IO thread.
@@ skipping 98 matching lines @@
   //             http://crbug.com/116139
   base::Lock watching_dns_lock_;
   bool watching_dns_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifier);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_H_