Made notification center notifications collapsed and expandable.

ui/message_center/message_center_tray.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_MESSAGE_CENTER_TRAY_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_TRAY_H_
 
 #include "base/observer_list.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/message_center_export.h"
@@ skipping 33 matching lines @@
   void ShowPopupBubble();
 
   // Returns whether the popup was visible before.
   bool HidePopupBubble();
 
   bool message_center_visible() { return message_center_visible_; }
   bool popups_visible() { return popups_visible_; }
   MessageCenterTrayDelegate* delegate() { return delegate_; }
   message_center::MessageCenter* message_center() { return message_center_; }
 
-  // Overridden from message_center::MessageCenter::Observer.
+  // Overridden from message_center::MessageCenter::Observer:
   virtual void OnMessageCenterChanged(bool new_notification) OVERRIDE;
 
  private:
   void NotifyMessageCenterTrayChanged();
 
   // |message_center_| is a weak pointer that must live longer than
   // MessageCenterTray.
   message_center::MessageCenter* message_center_;
   bool message_center_visible_;
   bool popups_visible_;
   // |delegate_| is a weak pointer that must live longer than MessageCenterTray.
   MessageCenterTrayDelegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageCenterTray);
 };
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_TRAY_H_