Draft change to use base::Closure instead of PrefObserver in PrefChangeRegistrar.

base/prefs/public/pref_change_registrar.h

 // Copyright (c) 2010 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_PREFS_PUBLIC_PREF_CHANGE_REGISTRAR_H_
 #define BASE_PREFS_PUBLIC_PREF_CHANGE_REGISTRAR_H_
 
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/prefs/base_prefs_export.h"
 
 class PrefObserver;
 class PrefServiceBase;
 
 // Automatically manages the registration of one or more pref change observers
 // with a PrefStore. Functions much like NotificationRegistrar, but specifically
 // manages observers of preference changes. When the Registrar is destroyed,
 // all registered observers are automatically unregistered with the PrefStore.
 class BASE_PREFS_EXPORT PrefChangeRegistrar {
  public:
   PrefChangeRegistrar();
   virtual ~PrefChangeRegistrar();
 
   // Must be called before adding or removing observers. Can be called more
   // than once as long as the value of |service| doesn't change.
   void Init(PrefServiceBase* service);
 
   // Adds an pref observer for the specified pref |path| and |obs| observer
   // object. All registered observers will be automatically unregistered
   // when the registrar's destructor is called unless the observer has been
   // explicitly removed by a call to Remove beforehand.
   void Add(const char* path, PrefObserver* obs);
+  void Add(const char* path, const base::Closure& obs);
 
-  // Removes a preference observer that has previously been added with a call to
-  // Add.
+  // Removes a preference observer that has previously been added with
+  // a call to Add. Note that in the base::Callback version of this
+  // method, you must pass an object whose Equal() method returns true
+  // when compared to the callback you registered via Add().
   void Remove(const char* path, PrefObserver* obs);
+  void Remove(const char* path, const base::Closure& obs);
 
   // Removes all observers that have been previously added with a call to Add.
   void RemoveAll();
 
   // Returns true if no pref observers are registered.
   bool IsEmpty() const;
 
   // Check whether |pref| is in the set of preferences being observed.
   bool IsObserved(const std::string& pref);
 
   // Check whether any of the observed preferences has the managed bit set.
   bool IsManaged();
 
  private:
-  typedef std::pair<std::string, PrefObserver*> ObserverRegistration;
+  typedef std::pair<std::string, base::Closure> ObserverRegistration;
 
   std::set<ObserverRegistration> observers_;
   PrefServiceBase* service_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
 };
 
 #endif  // BASE_PREFS_PUBLIC_PREF_CHANGE_REGISTRAR_H_