Avoid doing concurrent DNS resolves of the same hostname

net/http/http_network_session.h

Index: net/http/http_network_session.h
===================================================================
--- net/http/http_network_session.h	(revision 18213)
+++ net/http/http_network_session.h	(working copy)
@@ -13,21 +13,24 @@
 namespace net {
 
 class ClientSocketFactory;
+class HostResolver;
 class ProxyService;
 
 // This class holds session objects used by HttpNetworkTransaction objects.
 class HttpNetworkSession : public base::RefCounted<HttpNetworkSession> {
  public:
-  HttpNetworkSession(ProxyService* proxy_service,
+  HttpNetworkSession(HostResolver* host_resolver, ProxyService* proxy_service,
                      ClientSocketFactory* client_socket_factory)
       : connection_pool_(new TCPClientSocketPool(
-            max_sockets_per_group_, client_socket_factory)),
+            max_sockets_per_group_, host_resolver, client_socket_factory)),
+        host_resolver_(host_resolver),
         proxy_service_(proxy_service) {
     DCHECK(proxy_service);
   }
 
   HttpAuthCache* auth_cache() { return &auth_cache_; }
   ClientSocketPool* connection_pool() { return connection_pool_; }
+  HostResolver* host_resolver() { return host_resolver_; }
   ProxyService* proxy_service() { return proxy_service_; }
 #if defined(OS_WIN)
   SSLConfigService* ssl_config_service() { return &ssl_config_service_; }
@@ -43,6 +46,7 @@
 
   HttpAuthCache auth_cache_;
   scoped_refptr<ClientSocketPool> connection_pool_;
+  HostResolver* host_resolver_;
   ProxyService* proxy_service_;
 #if defined(OS_WIN)
   // TODO(port): Port the SSLConfigService class to Linux and Mac OS X.