WifiMetrics: add metric for alert reasons

Add metric to track the number of alerts triggered
by Wifi driver/firmware. This will give us a
concrete measurement of stability in the field.

BUG=29158746
TEST=tests/wifitests/runtests.sh

Change-Id: I435e5d792a97c197fe685e5b2c05d7b8efda62f0
5 files changed
tree: ca46597c92844f9af5d9f359c95b441cb4475d4f
  1. service/
  2. tests/