Revert of Move base/prefs to components/prefs

components/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 BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
-#define BASE_PREFS_PREF_CHANGE_REGISTRAR_H_
-
-#include <map>
-#include <string>
-
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/prefs/base_prefs_export.h"
-#include "base/prefs/pref_observer.h"
-
-class PrefService;
-
-// 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 PrefObserver {
- public:
-  // You can register this type of callback if you need to know the
-  // path of the preference that is changing.
-  typedef base::Callback<void(const std::string&)> NamedChangeCallback;
-
-  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 a 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.
-  //
-  // The second version binds a callback that will receive the path of
-  // the preference that is changing as its parameter.
-  //
-  // Only one observer may be registered per path.
-  void Add(const std::string& path, const base::Closure& obs);
-  void Add(const std::string& path, const NamedChangeCallback& obs);
-
-  // Removes the pref observer registered for |path|.
-  void Remove(const std::string& path);
-
-  // 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();
-
-  // Return the PrefService for this registrar.
-  PrefService* prefs();
-  const PrefService* prefs() const;
-
- private:
-  // PrefObserver:
-  void OnPreferenceChanged(PrefService* service,
-                           const std::string& pref_name) override;
-
-  static void InvokeUnnamedCallback(const base::Closure& callback,
-                                    const std::string& pref_name);
-
-  typedef std::map<std::string, NamedChangeCallback> ObserverMap;
-
-  ObserverMap observers_;
-  PrefService* service_;
-
-  DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
-};
-
-#endif  // BASE_PREFS_PREF_CHANGE_REGISTRAR_H_