Emit SignalStrengthChanged DBus signal when signal strength changes.

This CL modifies NetworkDBusAdaptor::UpdateProperties to emit
Network.SignalStrengthChanged DBus signal when the value of signal
strength has changed.

BUG=chrome-os-partner:9831
TEST=Monitor SignalStrengthChanged signals when the signal strength changes.

Change-Id: I06e6921378640fda77dd2e16dfc3521fd86c358e
Reviewed-on: https://gerrit.chromium.org/gerrit/23136
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
1 file changed