Make libfutures_channel available to DnsResolver Test: TH Bug 155855709 Original-Change: https://android-review.googlesource.com/1741281 Merged-In: Ie0088f08ecf0ce9201a48a5b8f0a575291c0e7cb Change-Id: Ie0088f08ecf0ce9201a48a5b8f0a575291c0e7cb