Currently the Request.cache attribute reflects the request's RequestCache setting. The current specs are a bit vague on this point. Only fetch() actually sets this, but the browser can bypass the http cache for other reasons. For example, if a user presses the refresh button causing the page to reload with http cache revalidation, should the corresponding FetchEvent.request.cache be set to no-cache.

I believe we should reflect these browser cache settings on all FetchEvent's whether they come from fetch() or another source.