net: plumb DnsRRResolver from IOThread to HttpNetworkSession.

chrome/browser/net/chrome_url_request_context.h

Index: chrome/browser/net/chrome_url_request_context.h
diff --git a/chrome/browser/net/chrome_url_request_context.h b/chrome/browser/net/chrome_url_request_context.h
index eccf82372ffe778483acc4b27c2c512409c68031..183ad4a93e43fcfb3ee6c6191bc6f1274af41c30 100644
--- a/chrome/browser/net/chrome_url_request_context.h
+++ b/chrome/browser/net/chrome_url_request_context.h
@@ -127,6 +127,9 @@ class ChromeURLRequestContext : public URLRequestContext {
   void set_host_resolver(net::HostResolver* resolver) {
     host_resolver_ = resolver;
   }
+  void set_dnsrr_resolver(net::DnsRRResolver* dnsrr_resolver) {
+    dnsrr_resolver_ = dnsrr_resolver;
+  }
   void set_http_transaction_factory(net::HttpTransactionFactory* factory) {
     http_transaction_factory_ = factory;
   }