Draft change to use base::Closure instead of PrefObserver in PrefChangeRegistrar.

base/prefs/public/pref_change_registrar.h

Index: base/prefs/public/pref_change_registrar.h
diff --git a/base/prefs/public/pref_change_registrar.h b/base/prefs/public/pref_change_registrar.h
index f3abd9869191056aedecb8a731f499c94414f521..8d9d8dd6b1d10e85b5bf963f9df56331a8e958d8 100644
--- a/base/prefs/public/pref_change_registrar.h
+++ b/base/prefs/public/pref_change_registrar.h
@@ -9,6 +9,7 @@
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/prefs/base_prefs_export.h"
 
 class PrefObserver;
@@ -32,10 +33,14 @@ class BASE_PREFS_EXPORT PrefChangeRegistrar {
   // when the registrar's destructor is called unless the observer has been
   // explicitly removed by a call to Remove beforehand.
   void Add(const char* path, PrefObserver* obs);
+  void Add(const char* path, const base::Closure& obs);
 
-  // Removes a preference observer that has previously been added with a call to
-  // Add.
+  // Removes a preference observer that has previously been added with
+  // a call to Add. Note that in the base::Callback version of this
+  // method, you must pass an object whose Equal() method returns true
+  // when compared to the callback you registered via Add().
   void Remove(const char* path, PrefObserver* obs);
+  void Remove(const char* path, const base::Closure& obs);
 
   // Removes all observers that have been previously added with a call to Add.
   void RemoveAll();
@@ -50,7 +55,7 @@ class BASE_PREFS_EXPORT PrefChangeRegistrar {
   bool IsManaged();
 
  private:
-  typedef std::pair<std::string, PrefObserver*> ObserverRegistration;
+  typedef std::pair<std::string, base::Closure> ObserverRegistration;
 
   std::set<ObserverRegistration> observers_;
   PrefServiceBase* service_;