This makes it easier to test, e.g. we can mock
DepotToolsClient.BatchListOwners without having to
mock DepotToolsClient first (to avoid initialization).

Change-Id: I9c24ef28ba7a82cd1498e863cc1b4bc825a579d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2616900Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>