Make libfutures_channel available to DnsResolver

Test: TH
Bug 155855709

Original-Change: https://android-review.googlesource.com/1741281
Merged-In: Ie0088f08ecf0ce9201a48a5b8f0a575291c0e7cb
Change-Id: Ie0088f08ecf0ce9201a48a5b8f0a575291c0e7cb
2 files changed