Improve spelling of "notification".

ui/message_center/message_center.h

 // Copyright (c) 2012 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_MESSAGE_CENTER_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 47 matching lines @@
   // Gets all notifications to be shown to the user in the message center.  Note
   // that queued changes due to the message center being open are not reflected
   // in this list.
   virtual const NotificationList::Notifications& GetVisibleNotifications() = 0;
 
   // Gets all notifications being shown as popups.  This should not be affected
   // by the change queue since notifications are not held up while the state is
   // VISIBILITY_TRANSIENT or VISIBILITY_SETTINGS.
   virtual NotificationList::PopupNotifications GetPopupNotifications() = 0;
 
-  // Management of NotificaitonBlockers.
+  // Management of NotificationBlockers.
   virtual void AddNotificationBlocker(NotificationBlocker* blocker) = 0;
   virtual void RemoveNotificationBlocker(NotificationBlocker* blocker) = 0;
 
   // Basic operations of notification: add/remove/update.
 
   // Adds a new notification.
   virtual void AddNotification(scoped_ptr<Notification> notification) = 0;
 
   // Updates an existing notification with id = old_id and set its id to new_id.
   virtual void UpdateNotification(
@@ skipping 84 matching lines @@
   MessageCenter();
   virtual ~MessageCenter();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MessageCenter);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_H_