Remove usage of FOR_EACH_OBSERVER macro in ui/message_center

ui/message_center/notification_blocker.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/message_center/notification_blocker.h"
 
 #include "ui/message_center/message_center.h"
 
 namespace message_center {
 
@@ skipping 16 matching lines @@
     NotificationBlocker::Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
 bool NotificationBlocker::ShouldShowNotification(
     const Notification& notification) const {
   return true;
 }
 
 void NotificationBlocker::NotifyBlockingStateChanged() {
-  FOR_EACH_OBSERVER(
-      NotificationBlocker::Observer, observers_, OnBlockingStateChanged(this));
+  for (auto& observer : observers_)
+    observer.OnBlockingStateChanged(this);
 }
 
 }  // namespace message_center