Do not allow CORS responses to "same-origin" requests

This matches the change in the Fetch spec:
https://github.com/whatwg/fetch/issues/629

This CL also removes the UseCounter for cross-origin CORS responses to
same-origin requests because it will be unreachable after hereafter.

Chrome status: https://www.chromestatus.com/feature/5694278818856960

Bug: 800234, 784018
Change-Id: Id843a302fa5d0614de1c3ef1c0a39bcf92f7e3ef
Reviewed-on: https://chromium-review.googlesource.com/866849
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Tsuyoshi Horo <horo@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Yannic Bonenberger <contact@yannic-bonenberger.com>
Cr-Commit-Position: refs/heads/master@{#531594}
8 files changed