Remove the last usages of PrefObserver outside of Prefs.

base/prefs/public/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_PUBLIC_PREF_CHANGE_REGISTRAR_H_
 #define BASE_PREFS_PUBLIC_PREF_CHANGE_REGISTRAR_H_
 
 #include <map>
 #include <string>
 
@@ skipping 25 matching lines @@
   // 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 char* path, const base::Closure& obs);
   void Add(const char* path, const NamedChangeCallback& obs);
 
-  // Deprecated version of Add, soon to be removed.
-  void Add(const char* path, PrefObserver* obs);
-
   // Removes the pref observer registered for |path|.
   void Remove(const char* 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.
@@ skipping 15 matching lines @@
 
   typedef std::map<std::string, NamedChangeCallback> ObserverMap;
 
   ObserverMap observers_;
   PrefServiceBase* service_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefChangeRegistrar);
 };
 
 #endif  // BASE_PREFS_PUBLIC_PREF_CHANGE_REGISTRAR_H_