net: plumb DnsRRResolver from IOThread to HttpNetworkSession.

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 2b55f6e8275ff44e9cdc8bd522cd5a6ba856402d..b76e89535c46d90e42e9a773f29a079fb79f876a 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -18,6 +18,7 @@
 #include "chrome/browser/net/passive_log_collector.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/net/url_fetcher.h"
+#include "net/base/dnsrr_resolver.h"
 #include "net/base/mapped_host_resolver.h"
 #include "net/base/host_cache.h"
 #include "net/base/host_resolver.h"
@@ -171,6 +172,7 @@ void IOThread::Init() {
 
   globals_->host_resolver.reset(
       CreateGlobalHostResolver(globals_->net_log.get()));
+  globals_->dnsrr_resolver.reset(new net::DnsRRResolver);
   globals_->http_auth_handler_factory.reset(CreateDefaultAuthHandlerFactory(
       globals_->host_resolver.get()));
 }