Support notifications with custom content

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
new file mode 100644
index 0000000000000000000000000000000000000000..6f993d2c640f5d42c4f2eb0f94cc03cf8ca95bc1
--- /dev/null
+++ b/ui/message_center/notification_delegate_views.cc
@@ -0,0 +1,15 @@
+// Copyright 2016 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.
+
+#include "ui/message_center/notification_delegate.h"
+
+#include "ui/views/view.h"
+
+namespace message_center {
+
+std::unique_ptr<views::View> NotificationDelegate::CreateCustomContent() {
+  return std::unique_ptr<views::View>();
+}
+
+}  // namespace message_center