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

chrome/browser/prefs/pref_notifier_impl.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 CHROME_BROWSER_PREFS_PREF_NOTIFIER_IMPL_H_
 #define CHROME_BROWSER_PREFS_PREF_NOTIFIER_IMPL_H_
 
 #include <list>
 #include <string>
 
 #include "base/callback.h"
 #include "base/hash_tables.h"
 #include "base/observer_list.h"
 #include "base/prefs/pref_notifier.h"
-#include "base/prefs/public/pref_observer.h"
 #include "base/threading/non_thread_safe.h"
 
 class PrefService;
 
 // The PrefNotifier implementation used by the PrefService.
 class PrefNotifierImpl : public PrefNotifier,
                          public base::NonThreadSafe {
  public:
   PrefNotifierImpl();
   explicit PrefNotifierImpl(PrefService* pref_service);
   virtual ~PrefNotifierImpl();
 
   // If the pref at the given path changes, we call the observer's
   // OnPreferenceChanged method.
-  void AddPrefObserver(const char* path, PrefObserver* observer);
-  void RemovePrefObserver(const char* path, PrefObserver* observer);
+  void AddPrefObserver(const char* path, const base::Closure& observer);
+
+  // This removes an observer.  Note that when using the Closure
+  // version of the method, you must provide a closure whose Equal()
+  // method will evaluate to true when compared to the closure you
+  // registered using AddPrefObserver.
+  void RemovePrefObserver(const char* path, const base::Closure& observer);
 
   // We run the callback once, when initialization completes. The bool
   // parameter will be set to true for successful initialization,
   // false for unsuccessful.
   void AddInitObserver(base::Callback<void(bool)> observer);
 
   void SetPrefService(PrefService* pref_service);
 
  protected:
   // PrefNotifier overrides.
   virtual void OnPreferenceChanged(const std::string& pref_name) OVERRIDE;
   virtual void OnInitializationCompleted(bool succeeded) OVERRIDE;
 
   // A map from pref names to a list of observers. Observers get fired in the
   // order they are added. These should only be accessed externally for unit
   // testing.
-  typedef ObserverList<PrefObserver> PrefObserverList;
+  typedef std::list<base::Closure> PrefObserverList;
   typedef base::hash_map<std::string, PrefObserverList*> PrefObserverMap;
 
   typedef std::list<base::Callback<void(bool)> > PrefInitObserverList;
 
   const PrefObserverMap* pref_observers() const { return &pref_observers_; }
 
  private:
   // For the given pref_name, fire any observer of the pref. Virtual so it can
   // be mocked for unit testing.
   virtual void FireObservers(const std::string& path);
 
   // Weak reference; the notifier is owned by the PrefService.
   PrefService* pref_service_;
 
   PrefObserverMap pref_observers_;
   PrefInitObserverList init_observers_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefNotifierImpl);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_NOTIFIER_IMPL_H_