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

ui/message_center/notification_delegate_views.cc

Index: ui/message_center/notification_delegate_views.cc
diff --git a/ui/message_center/notification_delegate_views.cc b/ui/message_center/notification_delegate_views.cc
index 6f993d2c640f5d42c4f2eb0f94cc03cf8ca95bc1..1d12a307f0813d5bdc52c49ea854d01987af809f 100644
--- a/ui/message_center/notification_delegate_views.cc
+++ b/ui/message_center/notification_delegate_views.cc
@@ -8,8 +8,8 @@
 
 namespace message_center {
 
-std::unique_ptr<views::View> NotificationDelegate::CreateCustomContent() {
-  return std::unique_ptr<views::View>();
+std::unique_ptr<CustomContent> NotificationDelegate::CreateCustomContent() {
+  return nullptr;
 }
 
 }  // namespace message_center