proving_grounds: Checkin code for go/wifi-down dashboard

BUG=None
TEST=None

Change-Id: Ifa8a80b09e89b8556ad5f80f69dfcc86e21b850e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crostestutils/+/3084226
Tested-by: Shijin Abraham <shijinabraham@google.com>
Reviewed-by: Harpreet Grewal <harpreet@chromium.org>
Commit-Queue: Shijin Abraham <shijinabraham@google.com>
8 files changed