Avoid doing concurrent DNS resolves of the same hostname

net/http/http_network_layer.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/http/http_network_layer.h"
 
 #include "base/logging.h"
 #include "net/base/client_socket_factory.h"
 #include "net/http/http_network_session.h"
 #include "net/http/http_network_transaction.h"
 
 namespace net {
 
 //-----------------------------------------------------------------------------
 
 // static
 HttpTransactionFactory* HttpNetworkLayer::CreateFactory(
+    HostResolver* host_resolver,
     ProxyService* proxy_service) {
   DCHECK(proxy_service);
 
-  return new HttpNetworkLayer(proxy_service);
+  return new HttpNetworkLayer(host_resolver, proxy_service);
 }
 
 // static
 HttpTransactionFactory* HttpNetworkLayer::CreateFactory(
     HttpNetworkSession* session) {
   DCHECK(session);
 
   return new HttpNetworkLayer(session);
 }
 
 //-----------------------------------------------------------------------------
 
-HttpNetworkLayer::HttpNetworkLayer(ProxyService* proxy_service)
-    : proxy_service_(proxy_service), session_(NULL), suspended_(false) {
+HttpNetworkLayer::HttpNetworkLayer(HostResolver* host_resolver,
+                                   ProxyService* proxy_service)
+    : host_resolver_(host_resolver),
+      proxy_service_(proxy_service),
+      session_(NULL),
+      suspended_(false) {
   DCHECK(proxy_service_);
 }
 
 HttpNetworkLayer::HttpNetworkLayer(HttpNetworkSession* session)
     : proxy_service_(NULL), session_(session), suspended_(false) {
   DCHECK(session_.get());
 }
 
 HttpNetworkLayer::~HttpNetworkLayer() {
 }
@@ skipping 13 matching lines @@
 void HttpNetworkLayer::Suspend(bool suspend) {
   suspended_ = suspend;
 
   if (suspend && session_)
     session_->connection_pool()->CloseIdleSockets();
 }
 
 HttpNetworkSession* HttpNetworkLayer::GetSession() {
   if (!session_) {
     DCHECK(proxy_service_);
-    session_ = new HttpNetworkSession(proxy_service_,
+    session_ = new HttpNetworkSession(host_resolver_, proxy_service_,
                                       ClientSocketFactory::GetDefaultFactory());
   }
   return session_;
 }
 
 }  // namespace net