text: // 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_DEFAULT_PREF_STORE_H_
  #define BASE_PREFS_DEFAULT_PREF_STORE_H_
  
  #include <string>
  
  #include "base/observer_list.h"
  #include "base/prefs/base_prefs_export.h"
  #include "base/prefs/pref_store.h"
  #include "base/prefs/pref_value_map.h"
  #include "base/values.h"
  
  // Used within a PrefRegistry to keep track of default preference values.
  class BASE_PREFS_EXPORT DefaultPrefStore : public PrefStore {
   public:
    typedef PrefValueMap::const_iterator const_iterator;
  
    DefaultPrefStore();
  
    // PrefStore implementation:
    bool GetValue(const std::string& key,
                  const base::Value** result) const override;
    void AddObserver(PrefStore::Observer* observer) override;
    void RemoveObserver(PrefStore::Observer* observer) override;
    bool HasObservers() const override;
  
    // Sets a |value| for |key|. Should only be called if a value has not been
    // set yet; otherwise call ReplaceDefaultValue().
    void SetDefaultValue(const std::string& key, std::unique_ptr<base::Value> value);
  
    // Replaces the the value for |key| with a new value. Should only be called
    // if a value has alreday been set; otherwise call SetDefaultValue().
    void ReplaceDefaultValue(const std::string& key,
                             std::unique_ptr<base::Value> value);
  
    const_iterator begin() const;
    const_iterator end() const;
  
   private:
    ~DefaultPrefStore() override;
  
    PrefValueMap prefs_;
  
    ObserverList<PrefStore::Observer, true> observers_;
  
    DISALLOW_COPY_AND_ASSIGN(DefaultPrefStore);
  };
  
  #endif  // BASE_PREFS_DEFAULT_PREF_STORE_H_
  