Temporarily change bgscan threshold in MultiSwitchBack

Temporarily change bgscan threshold in MultiSwitchBack

This makes the test more reliable by making it more
sensitive to the AP's change in signal level.  Also
use new method to reset background scan parameters
back to default after connection is made.

BUG=chromium-os:13938
TEST=Rerun test

Change-Id: I9abea39ee11177ffb876a75f6d1990270fbb7f4a

R=sleffler@chromium.org

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=46877f6

[Sam Leffler, 2011-04-07 19:08:06]

What changed that required futzing with the threshold?

http://codereview.chromium.org/6805027/diff/1/server/site_tests/network_WiFiR...
File server/site_tests/network_WiFiRoaming/003SSIDMultiSwitchBack (right):

http://codereview.chromium.org/6805027/diff/1/server/site_tests/network_WiFiR...
server/site_tests/network_WiFiRoaming/003SSIDMultiSwitchBack:16: [ "bgscan_set",
    { "signal":"-40" }],
maybe this belongs in the config file and set outside the tests?

[Paul Stewart, 2011-04-07 21:16:00]

Made the comment more explicit.  I think that the threshold has always been a
little flaky but something between the hardware refresh of the wndr3700s and the
new firmware made it a little flakier.  I've changed the comment to explain why
that threshold is set.

http://codereview.chromium.org/6805027/diff/1/server/site_tests/network_WiFiR...
File server/site_tests/network_WiFiRoaming/003SSIDMultiSwitchBack (right):

http://codereview.chromium.org/6805027/diff/1/server/site_tests/network_WiFiR...
server/site_tests/network_WiFiRoaming/003SSIDMultiSwitchBack:16: [ "bgscan_set",
    { "signal":"-40" }],
On 2011/04/07 19:08:06, Sam Leffler wrote:
> maybe this belongs in the config file and set outside the tests?

This is just a setup so that the "low signal" alert triggers reliably when I
vary the transmit power on the AP.  I don't think (yet) that this is widely
applicable to other tests than this one.  Changing the comment to be more
explicit.

[Sam Leffler, 2011-04-07 21:32:37]

LGTM