[ServiceWorker] window.fetch (#581)

List of issues blocking expose of `window.fetch`
- [ ] #535 `[Replaceable]`
- [ ] Restrict acceptable values for RequestInit.mode
- [ ] It's fine that we cannot choose CORS-with-forced-preflight?

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I'd like to start a tracking issue to sort out issues need to be resolved to expose `fetch()` on `window`.

Regarding RequestInit.mode, I guess we can accept `"same-origin"` and `"cors"`. Right? Reading the history of forced-preflight (http://dev.w3.org/cvsweb/2006/webapi/XMLHttpRequest-2/Overview.src.html#rev1.40), I guess that we don't need any option to choose with-forced-preflight.

It seems `mode` == `no CORS` is not meaningful in window. Should we allow this? With opaque filtering, it should be safe even if we accept it?

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Reply to this email directly or view it on GitHub:
https://github.com/slightlyoff/ServiceWorker/issues/581