Modify factory_AudioLoop messages

Add an option to toggle display require audio dongle
messages.

BUG=None
TEST=Manual run factory_AudioLoop, with 'require_dongle'
on or off, can see different message on factory UI.

Change-Id: I81345e27bdffdac617f6289a0d3a111f359566cc
Reviewed-on: https://gerrit.chromium.org/gerrit/48777
Commit-Queue: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
3 files changed