Add test showing "about:blank" is a unique Origin

This tripped me up for a second so I went looking in unit tests
for documentation.

Bug: None
Change-Id: If2e3c965e98a76d200afb4a1367141ee266ea715
Reviewed-on: https://chromium-review.googlesource.com/1136457
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575235}
1 file changed