Introduce incognito preference settings.

chrome/browser/prefs/pref_member.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.
 //
 // A helper class that stays in sync with a preference (bool, int, real,
 // string or filepath).  For example:
 //
 // class MyClass {
 //  public:
 //   MyClass(PrefService* prefs) {
@@ skipping 27 matching lines @@
 class PrefMemberBase : public NotificationObserver {
  protected:
   PrefMemberBase();
   virtual ~PrefMemberBase();
 
   // See PrefMember<> for description.
   void Init(const char* pref_name, PrefService* prefs,
             NotificationObserver* observer);
 
   // See PrefMember<> for description.
+  void Destroy();
+
+  // See PrefMember<> for description.
   bool IsManaged() const;
 
   // NotificationObserver
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
 
   void VerifyValuePrefName() const;
 
   // This methods is used to do the actual sync with pref of the specified type.
@@ skipping 27 matching lines @@
   PrefMember() : value_(ValueType()) {}
   virtual ~PrefMember() {}
 
   // Do the actual initialization of the class.  |observer| may be null if you
   // don't want any notifications of changes.
   void Init(const char* pref_name, PrefService* prefs,
             NotificationObserver* observer) {
     subtle::PrefMemberBase::Init(pref_name, prefs, observer);
   }
 
+  // Unsubscribes the PrefMember from the PrefService. After calling this
+  // function, the PrefMember may not be used any more.
+  void Destroy() {
+    subtle::PrefMemberBase::Destroy();
+  }
+
   // Check whether the pref is managed, i.e. controlled externally through
   // enterprise configuration management (e.g. windows group policy). Returns
   // false for unknown prefs.
   bool IsManaged() {
     return subtle::PrefMemberBase::IsManaged();
   }
 
   // Retrieve the value of the member variable.
   ValueType GetValue() const {
     VerifyValuePrefName();
@@ skipping 97 matching lines @@
 
  protected:
   virtual void UpdateValueFromPref() const;
   virtual void UpdatePref(const FilePath& value);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FilePathPrefMember);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_MEMBER_H_