Network service support for non-address host resolution

Expanded the ResolveHostClient Mojo interface with additional
On...Results() methods to be called before OnComplete() when
non-address results are available.

Created a new ResolveHostClientBase abstract implementation, so client
implementations don't need to implement all these new methods if they
only expect certain result types.  Converted all the current client
implementations.

TBR=dgozman@chromium.org,alexilin@chromium.org,bbudge@chromium.org,tbarzic@chromium.org

Bug: 846423
Change-Id: Id84a1537c150a05f631545d0718a1236c6c4003e
Reviewed-on: https://chromium-review.googlesource.com/c/1378673
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@{#623314}
19 files changed