Revert of Move base/prefs to components/prefs

components/prefs/pref_store.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 BASE_PREFS_PREF_STORE_H_
-#define BASE_PREFS_PREF_STORE_H_
-
-#include <string>
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/prefs/base_prefs_export.h"
-
-namespace base {
-class Value;
-}
-
-// This is an abstract interface for reading and writing from/to a persistent
-// preference store, used by PrefService. An implementation using a JSON file
-// can be found in JsonPrefStore, while an implementation without any backing
-// store for testing can be found in TestingPrefStore. Furthermore, there is
-// CommandLinePrefStore, which bridges command line options to preferences and
-// ConfigurationPolicyPrefStore, which is used for hooking up configuration
-// policy with the preference subsystem.
-class BASE_PREFS_EXPORT PrefStore : public base::RefCounted<PrefStore> {
- public:
-  // Observer interface for monitoring PrefStore.
-  class BASE_PREFS_EXPORT Observer {
-   public:
-    // Called when the value for the given |key| in the store changes.
-    virtual void OnPrefValueChanged(const std::string& key) = 0;
-    // Notification about the PrefStore being fully initialized.
-    virtual void OnInitializationCompleted(bool succeeded) = 0;
-
-   protected:
-    virtual ~Observer() {}
-  };
-
-  PrefStore() {}
-
-  // Add and remove observers.
-  virtual void AddObserver(Observer* observer) {}
-  virtual void RemoveObserver(Observer* observer) {}
-  virtual bool HasObservers() const;
-
-  // Whether the store has completed all asynchronous initialization.
-  virtual bool IsInitializationComplete() const;
-
-  // Get the value for a given preference |key| and stores it in |*result|.
-  // |*result| is only modified if the return value is true and if |result|
-  // is not NULL. Ownership of the |*result| value remains with the PrefStore.
-  virtual bool GetValue(const std::string& key,
-                        const base::Value** result) const = 0;
-
- protected:
-  friend class base::RefCounted<PrefStore>;
-  virtual ~PrefStore() {}
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(PrefStore);
-};
-
-#endif  // BASE_PREFS_PREF_STORE_H_