Add Chromium for iOS test documentation.

Create documentation on how to run different iOS test suites.

TBR: huangml
Bug: 769753
Change-Id: I1e63c6c603a10389ccc89050b01e075fd08e39ae
Reviewed-on: https://chromium-review.googlesource.com/772784
Reviewed-by: Mike Baxley <baxley@chromium.org>
Commit-Queue: Mike Baxley <baxley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517095}
2 files changed