Update list of OWNERS for test runner library

BUG=none
R=abarth@chromium.org,dmazzoni@chromium.org,dpranke@chromium.org,pfeldman@chromium.org,tkent@chromium.org,tommyw@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/123253002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242773 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242773