Introduce incognito preference settings.

chrome/common/pref_store.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// 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_COMMON_PREF_STORE_H_
 #define CHROME_COMMON_PREF_STORE_H_
 #pragma once
 
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/ref_counted.h"
 
 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 PrefStore {
+class PrefStore : public base::RefCounted<PrefStore> {
  public:
   // Observer interface for monitoring PrefStore.
   class Observer {
    public:
     virtual ~Observer() {}
 
     // 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() = 0;
   };
 
   // Return values for GetValue().
   enum ReadResult {
     // Value found and returned.
     READ_OK,
     // No value present, but skip other pref stores and use default.
     READ_USE_DEFAULT,
     // No value present.
     READ_NO_VALUE,
   };
 
   PrefStore() {}
-  virtual ~PrefStore() {}
 
   // Add and remove observers.
   virtual void AddObserver(Observer* observer) {}
   virtual void RemoveObserver(Observer* observer) {}
 
   // 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 READ_OK. Ownership of the
   // |result| value remains with the PrefStore.
   virtual ReadResult GetValue(const std::string& key, Value** result) const = 0;
 
+ protected:
+  friend class base::RefCounted<PrefStore>;
+  virtual ~PrefStore() {}
+
+ private:
   DISALLOW_COPY_AND_ASSIGN(PrefStore);
 };
 
 #endif  // CHROME_COMMON_PREF_STORE_H_