Reland "Send SXG accept header of navigation only to limited origins for Origin Trial."

This reverts commit 4762a8308d63693404e76024be50b4d9d060ee6b.

The difference from the original patch is that in this patch
SignedExchangeAcceptHeaderBrowserTest uses SetUp() instead of
SetUpOnMainThread() to avoid the failures in TSAN bots.

Bug: 887201
TBR=kinuko@, kouhei@, ksakamoto@

Original change's description:
> Send SXG accept header of navigation only to limited origins for Origin Trial.
>
> Before this patch:
>   The SXG accept header is sent to all origins when SignedHTTPExchange feature
>   or SignedHTTPExchangeOriginTrial feature is enabled.
>
> After this patch:
>   The SXG accept header is sent when
>     - SignedHTTPExchange feature is enabled.
>     or
>     - SignedHTTPExchangeOriginTrial feature and SignedHTTPExchangeAcceptHeader
>       feature are enabled and the origin of the URL is in the OriginList of
>       SignedHTTPExchangeAcceptHeader field trial.
>
> Bug: 887201
> Change-Id: Ic67a8bc0644b1b6172030ff75162c04663dd33f0
> Reviewed-on: https://chromium-review.googlesource.com/1242768
> Reviewed-by: Kinuko Yasuda <[email protected]>
> Reviewed-by: Kunihiko Sakamoto <[email protected]>
> Reviewed-by: Kouhei Ueno <[email protected]>
> Commit-Queue: Tsuyoshi Horo <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#595002}

Change-Id: Iff188ffe2096c35d2c9fb4eee3723e78f5901b26
Reviewed-on: https://chromium-review.googlesource.com/1251144
Reviewed-by: Tsuyoshi Horo <[email protected]>
Commit-Queue: Tsuyoshi Horo <[email protected]>
Cr-Commit-Position: refs/heads/master@{#595065}
5 files changed