Fixes the policy to choose the notifications for popups.

ui/message_center/notification_list.h

Index: ui/message_center/notification_list.h
diff --git a/ui/message_center/notification_list.h b/ui/message_center/notification_list.h
index 87cf509dc5a7231b94c837496fee0430e5f60e72..bd97dbc0a1906f0ebb81c6c6dcd6fee340c1a82d 100644
--- a/ui/message_center/notification_list.h
+++ b/ui/message_center/notification_list.h
@@ -181,8 +181,8 @@ class MESSAGE_CENTER_EXPORT NotificationList {
   // as a popup. kMaxVisiblePopupNotifications are used to limit the number of
   // notifications for the default priority.
   void GetPopupIterators(int priority,
-                         Notifications::iterator& first,
-                         Notifications::iterator& last);
+                         Notifications::iterator* first,
+                         Notifications::iterator* last);
 
   // Given a dictionary of optional notification fields (or NULL), unpacks all
   // recognized values into the given Notification struct. We assume prior