The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c53b19a77794aec3c8d10ebd6552e7523d360a0d

commit c53b19a77794aec3c8d10ebd6552e7523d360a0d
Author: juliatuttle <juliatuttle@chromium.org>
Date: Thu May 05 13:51:31 2016

DNS: Support reprioritization of requests.

Add HostResolver::ChangeRequestPriority, and make HostResolverImpl
update the priority of a request when it's called.

Also add an empty stub to HostResolverMojo, since it appears to ignore
priorities at the moment.

Let other HostResolver subclasses hit a NOTIMPLEMENTED(), since it's a
brand new method nobody's using in tests.

BUG= 607296 

Review-Url: https://codereview.chromium.org/1928743003
Cr-Commit-Position: refs/heads/master@{#391797}

[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver.cc
[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver.h
[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver_impl.cc
[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver_impl.h
[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver_impl_unittest.cc
[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver_mojo.cc
[modify] https://crrev.com/c53b19a77794aec3c8d10ebd6552e7523d360a0d/net/dns/host_resolver_mojo.h