Initial implementation of new-style notification

ui/arc/notification/arc_notification_item_impl.h

Index: ui/arc/notification/arc_notification_item_impl.h
diff --git a/ui/arc/notification/arc_notification_item_impl.h b/ui/arc/notification/arc_notification_item_impl.h
index 2fbf31479c9ddac426cc293978dc0cb757249ebe..9f69b57bbd76a95f704c6ef0c5fa0d17fe0cb6d3 100644
--- a/ui/arc/notification/arc_notification_item_impl.h
+++ b/ui/arc/notification/arc_notification_item_impl.h
@@ -48,6 +48,7 @@ class ArcNotificationItemImpl : public ArcNotificationItem {
   mojom::ArcNotificationShownContents GetShownContents() const override;
   const std::string& GetNotificationKey() const override;
   const std::string& GetNotificationId() const override;
+  const base::string16& GetAccessibleName() const override;
 
  private:
   // Return true if it's on the thread this instance is created on.
@@ -68,6 +69,8 @@ class ArcNotificationItemImpl : public ArcNotificationItem {
       mojom::ArcNotificationShownContents::CONTENTS_SHOWN;
   // The reference counter of the window.
   int window_ref_count_ = 0;
+  // The accessible name of the latest notification.
+  base::string16 accessible_name_;
 
   base::ObserverList<Observer> observers_;