Remove content::NotificationObserver dependency from most Prefs code.

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 97743e2317464aced22c0ce2c055139398b081c9..730f2afc350f4c2a047677582a276f693e77edd3 100644
--- a/base/prefs/public/pref_change_registrar.h
+++ b/base/prefs/public/pref_change_registrar.h
@@ -10,12 +10,9 @@
 
 #include "base/basictypes.h"
 
+class PrefObserver;
 class PrefServiceBase;
 
-namespace content {
-class NotificationObserver;
-}
-
 // Automatically manages the registration of one or more pref change observers
 // with a PrefStore. Functions much like NotificationRegistrar, but specifically
 // manages observers of preference changes. When the Registrar is destroyed,
@@ -33,13 +30,11 @@ class PrefChangeRegistrar {
   // object. All registered observers will be automatically unregistered
   // 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,
-           content::NotificationObserver* obs);
+  void Add(const char* path, PrefObserver* obs);
 
   // Removes a preference observer that has previously been added with a call to
   // Add.
-  void Remove(const char* path,
-              content::NotificationObserver* obs);
+  void Remove(const char* path, PrefObserver* obs);
 
   // Removes all observers that have been previously added with a call to Add.
   void RemoveAll();
@@ -54,8 +49,7 @@ class PrefChangeRegistrar {
   bool IsManaged();
 
  private:
-  typedef std::pair<std::string, content::NotificationObserver*>
-      ObserverRegistration;
+  typedef std::pair<std::string, PrefObserver*> ObserverRegistration;
 
   std::set<ObserverRegistration> observers_;
   PrefServiceBase* service_;