Places the unread count in the middle of web notification tray button.

ash/system/web_notification/web_notification_tray.h

Index: ash/system/web_notification/web_notification_tray.h
diff --git a/ash/system/web_notification/web_notification_tray.h b/ash/system/web_notification/web_notification_tray.h
index 7c4f01fb0b9ce6c64c7510c9cbb1f8e03819407e..13be8c6fc60eae1da520e8b70a057f2e1430073c 100644
--- a/ash/system/web_notification/web_notification_tray.h
+++ b/ash/system/web_notification/web_notification_tray.h
@@ -41,6 +41,7 @@ namespace ash {
 namespace internal {
 class StatusAreaWidget;
 class WebNotificationBubbleWrapper;
+class WebNotificationButton;
 }
 
 class ASH_EXPORT WebNotificationTray
@@ -142,7 +143,7 @@ class ASH_EXPORT WebNotificationTray
   scoped_ptr<internal::WebNotificationBubbleWrapper> popup_bubble_;
   scoped_ptr<message_center::MessagePopupCollection> popup_collection_;
   scoped_ptr<views::MenuRunner> quiet_mode_menu_runner_;
-  views::ImageButton* button_;
+  internal::WebNotificationButton* button_;
 
   bool show_message_center_on_unlock_;