Check that everything works with git nav-downstream, which we're not afraid of breaking

Bug: 832386
Change-Id: I7c7561c749bc72cc12804c4ebce8f827ed8be02b
Reviewed-on: https://chromium-review.googlesource.com/1134518Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>