Use PrefChangeRegistrar everywhere

chrome/browser/extensions/extension_toolbar_model.h

Index: chrome/browser/extensions/extension_toolbar_model.h
diff --git a/chrome/browser/extensions/extension_toolbar_model.h b/chrome/browser/extensions/extension_toolbar_model.h
index 028c8b5c39d8b5d8dff7b56e1c57c06216da3474..a38fc8c097a83c66118d90f049d205dc9aea514d 100644
--- a/chrome/browser/extensions/extension_toolbar_model.h
+++ b/chrome/browser/extensions/extension_toolbar_model.h
@@ -20,6 +20,10 @@ class ExtensionToolbarModel : public NotificationObserver {
   explicit ExtensionToolbarModel(ExtensionsService* service);
   ~ExtensionToolbarModel();
 
+  // Notifies the toolbar model that the Profile that suplied its
+  // prefs is being destroyed.
+  void DestroyingProfile();
+
   // A class which is informed of changes to the model; represents the view of
   // MVC.
   class Observer {