Add components/arc/metrics/OWNERS

BUG=b:116761000
TEST=None

Change-Id: Ibb780305e22e90b589aaeef535b7220182d3bb15
Reviewed-on: https://chromium-review.googlesource.com/1251224Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Maajid <maajid@chromium.org>
Commit-Queue: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595379}

components/arc/metrics/OWNERS

+maajid@chromium.org