Bug 1523562 [wpt PR 14985] - Support document.referrer in SXG, a=testonly

Bug 1523562 [wpt PR 14985] - Support document.referrer in SXG, a=testonly

Automatic update from web-platform-tests
Support document.referrer in SXG

Before this CL, CreateRedirectInfo() in signed_exchange_loader.cc doesn't set
redirect_info.new_referrer correctly. So document.referrer was always empty
string after clicking a link of signed exchange.
After this CL, CreateRedirectInfo() returns a RedirectInfo with new_referrer, so
document.referrer will be set correctly.

This CL introduces network::ResourceRequest argument in
NavigationLoaderInterceptor::MaybeCreateLoaderForResponse(),
PrefetchURLLoader, SignedExchangePrefetchHandler and SignedExchangeLoader.
This value will be used to compute a correct RedirectInfo while handling the
synthesized redirect for signed exchange.

This CL uses "ignoreErrors" flag in generate-test-sxgs.sh while creating invalid
signed exchange files. This flags was introduces by this change in webpackage
repository.
https://github.com/WICG/webpackage/commit/d3352199e0a074ef0ce4390232b861560d061425

Bug: 920905
Change-Id: I52a302d22c375b776874c996638b409cdcba8a9c
Reviewed-on: https://chromium-review.googlesource.com/c/1415245
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kunihiko Sakamoto <ksakamoto@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625094}

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wpt-commits: 5835a01f1f638f866215570119e88f9cac57e8c6
wpt-pr: 14985