A document loading for an iframe with srcdoc attribute doesn't go through fetch algorithm. (That is, it uses the given value instead of fetching a resource.) So currently the selection (match) of the service worker registration for the navigation doesn't occur.

In the recent service worker f2f, it has been discussed that once the iframe srcdoc document is created, the resource requests for that document should be controlled by the containing frame's service worker. This bit should be specified.

Related issue: w3c/ServiceWorker#765