Cookie Store: Consolidate WPT coverage for special prefixed cookies

Merge two sets of tests that cover __Secure- and __Host- prefixed
cookies in the API. Tests cover secure and non-secure contexts,
getting, setting, deleting, and setting already-expired cookies.

Bug: 729800
Change-Id: Ie7e84eeda03ba8192f5062cbf5240ff8ab13816a
Reviewed-on: https://chromium-review.googlesource.com/994174
Commit-Queue: Joshua Bell <jsbell@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548562}
8 files changed