DNS: Support reprioritization of requests.

net/dns/host_resolver_mojo.cc

Index: net/dns/host_resolver_mojo.cc
diff --git a/net/dns/host_resolver_mojo.cc b/net/dns/host_resolver_mojo.cc
index 1daf6338fd425bffd0ad1db3a6497b3f5d164325..d65a81e1cde63a5b0bd88b5e5727cfc18a0f2532 100644
--- a/net/dns/host_resolver_mojo.cc
+++ b/net/dns/host_resolver_mojo.cc
@@ -92,6 +92,11 @@ int HostResolverMojo::ResolveFromCache(const RequestInfo& info,
   return ResolveFromCacheInternal(info, CacheKeyForRequest(info), addresses);
 }
 
+void HostResolverMojo::ChangeRequestPriority(RequestHandle req,
+                                             RequestPriority priority) {
+  // Do nothing, since Resolve() discarded the priority anyway.
+}
+
 void HostResolverMojo::CancelRequest(RequestHandle req) {
   DCHECK(thread_checker_.CalledOnValidThread());
   // Deleting the Job closes the HostResolverRequestClient connection,