Async Cookies: Add idlharness test

Bug: 729800
Change-Id: If6cfed3427f778cf990721214240757cb06f320a
Reviewed-on: https://chromium-review.googlesource.com/912242
Commit-Queue: Joshua Bell <jsbell@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535928}
5 files changed