Move aom layout tests to using synchronous tests.

After multiple problems with running async_tests and them timing out, we
have decided to move all tests to just synchronous test runners.

BUG=792783

Change-Id: I300c94795ea0c9a657561916eccc86bbed0be0a9
Reviewed-on: https://chromium-review.googlesource.com/913051
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Meredith Lane <meredithl@google.com>
Cr-Commit-Position: refs/heads/master@{#536031}
4 files changed