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

base/prefs/public/pref_service_base.h

Index: base/prefs/public/pref_service_base.h
diff --git a/base/prefs/public/pref_service_base.h b/base/prefs/public/pref_service_base.h
index 131d221776b7e4345f0cc8aecf65b63bf48f945f..779b7b4c2e5c94a92ae80e8490df1c565050c6b8 100644
--- a/base/prefs/public/pref_service_base.h
+++ b/base/prefs/public/pref_service_base.h
@@ -16,6 +16,7 @@
 #ifndef BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_
 #define BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_
 
+#include "base/callback_forward.h"
 #include "base/values.h"
 
 namespace content {
@@ -259,12 +260,13 @@ class PrefServiceBase {
   // These are protected so they can only be accessed by the friend
   // classes listed above.
   //
-  // If the pref at the given path changes, we call the observer's
-  // OnPreferenceChanged method. Note that observers should not call
-  // these methods directly but rather use a PrefChangeRegistrar to
-  // make sure the observer gets cleaned up properly.
-  virtual void AddPrefObserver(const char* path, PrefObserver* obs) = 0;
-  virtual void RemovePrefObserver(const char* path, PrefObserver* obs) = 0;
+  // If the pref at the given path changes, we run the closure. Note
+  // that observers should not call these methods directly but rather
+  // use a PrefChangeRegistrar to make sure the observer gets cleaned
+  // up properly.
+  virtual void AddPrefObserver(const char* path, const base::Closure& obs) = 0;
+  virtual void RemovePrefObserver(const char* path,
+                                  const base::Closure& obs) = 0;
 };
 
 #endif  // BASE_PREFS_PUBLIC_PREF_SERVICE_BASE_H_