[Mac][MC] Implement notification updates and relayouts.

ui/message_center/cocoa/popup_controller.h

 // Copyright (c) 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.
 
 #ifndef UI_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_
 #define UI_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <string>
@@ skipping 14 matching lines @@
 MESSAGE_CENTER_EXPORT
 @interface MCPopupController : NSWindowController {
  @private
   scoped_nsobject<MCNotificationController> notificationController_;
 }
 
 // Designated initializer.
 - (id)initWithNotification:(const message_center::Notification*)notification
     messageCenter:(message_center::MessageCenter*)messageCenter;
 
-// Accessor for the notification.
+// Accessor for the view controller.
+- (MCNotificationController*)notificationController;
+
+// Accessor for the notification model object.
 - (const message_center::Notification*)notification;
 
 // Gets the notification ID. This string is owned by the NotificationController
 // rather than the model object, so it's safe to use after the Notification has
 // been deleted.
 - (const std::string&)notificationID;
 
 @end
 
 #endif  // UI_MESSAGE_CENTER_COCOA_POPUP_CONTROLLER_H_