Sends Updated when message center is closed.

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 852107d3a5907c97de4c9d90463c217d23c20a07..f69b18894c701e021cec06a406357587fca101a1 100644
--- a/ui/message_center/notification_list.h
+++ b/ui/message_center/notification_list.h
@@ -49,8 +49,11 @@ class MESSAGE_CENTER_EXPORT NotificationList {
   explicit NotificationList();
   virtual ~NotificationList();
 
-  // Affects whether or not a message has been "read".
-  void SetMessageCenterVisible(bool visible);
+  // Affects whether or not a message has been "read". Collects the set of
+  // ids whose state have changed and set to |udpated_ids|. NULL if updated
+  // ids don't matter.
+  void SetMessageCenterVisible(bool visible,
+                               std::set<std::string>* updated_ids);
 
   void AddNotification(NotificationType type,
                        const std::string& id,