chromium/chrome/test/data/extensions/api_test/service_worker/mime_handler_view/page_with_embed.html

<!--
 * Copyright 2018 The Chromium Authors
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
-->
The "ics" extension is hard-coded as "text/calendar" by net::MimeUtil.
So, regardless of the platform's MIME type for the "ics" file extension,
the resource will always be served as "text/calendar" and therefore be handled
by the test extension.
<embed src="well-known-mime.ics"></embed>