arc: Add OWNERS to c/b/c/arc/intent_helper/

djacobo@ owns c/b/c/apps/intent_helper/ already. This CL does the
same for c/b/c/arc/.

BUG=None
TEST=no code change

Change-Id: I732ab869f8cd1a58d833f81522e1653a12e4afcb
Reviewed-on: https://chromium-review.googlesource.com/994063Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Reviewed-by: David Jacobo <djacobo@chromium.org>
Commit-Queue: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547939}

chrome/browser/chromeos/arc/intent_helper/OWNERS

+djacobo@chromium.org