Add jennyz and stevenjb to the OWNERS list of app_list code.

BUG=NONE
R=xiyuan@chromium.org

Review URL: https://codereview.chromium.org/187943002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255079 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255079