Cookie Store: rework tests for 'expires' option

Simplify/rework the tests for the 'expires' options. Don't run the
tests with the special secure-only prefixes, as that's orthogonal to
the behvior.

In Chromium, this also reveals that support for HTTP date strings as
'expires' values, as described in the explainer[1] is not yet
supported.

[1] https://github.com/WICG/cookie-store/blob/gh-pages/explainer.md

Bug: 729800
Change-Id: I015fd643f18b59c8294f9dc62d576682132795fd
Reviewed-on: https://chromium-review.googlesource.com/994284
Commit-Queue: Joshua Bell <jsbell@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548818}
5 files changed