Move PrefMember and PrefChangeRegistrar to api directory.

chrome/browser/prefs/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 CHROME_BROWSER_PREFS_PREF_CHANGE_REGISTRAR_H_
-#define CHROME_BROWSER_PREFS_PREF_CHANGE_REGISTRAR_H_
-
-#include <set>
-#include <string>
-
-#include "base/basictypes.h"
-
-class PrefService;
-
-namespace content {
-class NotificationObserver;
-}
-
-// 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 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(PrefService* 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,
-           content::NotificationObserver* obs);
-
-  // Removes a preference observer that has previously been added with a call to
-  // Add.
-  void Remove(const char* path,
-              content::NotificationObserver* 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;
-
- private:
-  typedef std::pair<std::string, content::NotificationObserver*>
-      ObserverRegistration;
-
-  std::set<ObserverRegistration> observers_;
-  PrefService* service_;
-
-  DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
-};
-
-#endif  // CHROME_BROWSER_PREFS_PREF_CHANGE_REGISTRAR_H_