Modernize host resolution in SpdySessionPool

Includes fix for an affected test with brittle logic for determining
request IDs in MockHostResolver.  The new API has different effects on
the logic for generating such IDs.

Also fixed HangingHostResolver to always return ERR_DNS_CACHE_MISS when
source is LOCAL_ONLY to match HangingHostResolver::ResolveFromCache()
behavior.

Bug: 922699
Change-Id: I388dfc2a42feb49ca055160eb1bbcee05bb05de9
Reviewed-on: https://chromium-review.googlesource.com/c/1457215
Auto-Submit: Eric Orth <ericorth@chromium.org>
Commit-Queue: Asanka Herath <asanka@chromium.org>
Reviewed-by: Asanka Herath <asanka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632726}
4 files changed