Start with trying to spec foreign fetch.

[mkruisselbrink]

My attempt to spec the API described in issue #684.

I don't think this is anywhere near ready to be merged yet (in only because as far as I know current master is still V1, and this definitely is a V2 feature), but a pull request seemed like the easiest way to have a place to discuss details of foreign fetch.

Also haven't updated the .ts file with these changes, but then that file seems to be rather out of date anyway. So not sure if that file is still being used?

[annevk]

@jungkees did you read OP? "I don't think this is anywhere near ready to be merged yet"...

[jungkees]

@mkruisselbrink was waiting for V1 branching out. I reviewed and merged this PR to the nightly version. I think it's okay. A few minor fixes seem to be needed which I'll take care.

[jungkees]

@mkruisselbrink thanks for the excellent text. I made minor changes (ca15dee) especially in InstallEvent and its event.registerForeignFetchScopes(subScopes) steps. Note that I changed the parameter type of the method to sequence<USVString> in order to maintain consistency with other methods (such as cache.addAll(sequence<RequestInfo> requests)) in the spec.

[wanderview]

It still seems some time to review and discuss before merging to spec would be nice.

[jungkees]

Agreed and reverted the merge manually (3cc01ee) as I had already put some changes on it.

My apologies @mkruisselbrink. Could you make a PR again to the nightly version (the same file you made one)? Let's discuss and work on it. Thanks!