This is a consequence of mixed content and its integration with SW. See: https://github.com/whatwg/fetch/issues/69
Ehsan wonders if this is true for Shared Workers as well.
I don't think SharedWorkers can exist without a document attached, can they? I thought the SharedWorker was stopped when the last document closed.
They can exist with more than one Client...
Note: request window is defined here: <https://fetch.spec.whatwg.org/#concept-request-window>
We don't think this blocks v1 because currently the only way to get a service worker without a window is via a push event, which is separate from v1. Also, I think the spec has changed a bit here. It now has the concept of the associated window as an internal property on the Request. This would likely be reflected in our code by stashing the intercepted channel's loading document on InternalRequest and then using it for the FetchDriver channel.