Closed-loop audio feedback client implementation.

This is an implementation of a feedback client for interactive audio
testing that is based on a closed-loop connection between the DUT's
audio-out/audio-in jacks.  This includes logic for both playback and
recording queries.

BUG=b:26162596
TEST=None

Change-Id: I930630a9beedbdbc1d9c879aeb50c27285682116
Reviewed-on: https://chromium-review.googlesource.com/319198
Commit-Ready: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Ralph Nathan <ralphnathan@chromium.org>
5 files changed