autotest: Add a performance test

Add a performance test that takes measurements for a given set of router
configurations.  This test takes multiple measurements and calculates
measurement sample deviation.  Performance results are reported as
keyval pairs.

BUG=chromium:279395
TEST=This is a test.  The example control file measures HT40 performance
for both bands.

Change-Id: I1243b78c94c7f4e7137fdcb4224f89de6ea4df95
Reviewed-on: https://chromium-review.googlesource.com/169921
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
Tested-by: Christopher Wiley <wiley@chromium.org>
2 files changed