Service API for HostResolver MDNS listener

Bug: 922161
Change-Id: I33ba427d5449a0e93d36bdd9078d8a9b59b90422
Reviewed-on: https://chromium-review.googlesource.com/c/1413057
Commit-Queue: Eric Orth <ericorth@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Maks Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625337}
10 files changed