Transfer responsibility for providing a close button for a notification to each implementation of M…

ui/arc/notification/arc_custom_notification_view.h

Index: ui/arc/notification/arc_custom_notification_view.h
diff --git a/ui/arc/notification/arc_custom_notification_view.h b/ui/arc/notification/arc_custom_notification_view.h
index 5c29831f420ed653e92a55094dafae159a879d6c..949cdee886780f87be21b0e7f4391a858a2387aa 100644
--- a/ui/arc/notification/arc_custom_notification_view.h
+++ b/ui/arc/notification/arc_custom_notification_view.h
@@ -12,6 +12,7 @@
 #include "ui/arc/notification/arc_custom_notification_item.h"
 #include "ui/arc/notification/arc_notification_surface_manager.h"
 #include "ui/aura/window_observer.h"
+#include "ui/message_center/views/custom_notification_content_view_delegate.h"
 #include "ui/views/controls/button/button.h"
 #include "ui/views/controls/native/native_view_host.h"
 
@@ -36,7 +37,11 @@ class ArcCustomNotificationView
   explicit ArcCustomNotificationView(ArcCustomNotificationItem* item);
   ~ArcCustomNotificationView() override;
 
+  std::unique_ptr<message_center::CustomNotificationContentViewDelegate>
+  CreateContentViewDelegate();
+
  private:
+  class ContentViewDelegate;
   class EventForwarder;
   class SlideHelper;