Avoid doing concurrent DNS resolves of the same hostname

net/base/tcp_client_socket_pool.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/base/tcp_client_socket_pool.h"
 
 #include "base/compiler_specific.h"
 #include "base/field_trial.h"
 #include "base/message_loop.h"
 #include "base/time.h"
@@ skipping 28 matching lines @@
     const ClientSocketHandle* handle,
     ClientSocketFactory* client_socket_factory,
     TCPClientSocketPool* pool)
     : group_name_(group_name),
       handle_(handle),
       client_socket_factory_(client_socket_factory),
       ALLOW_THIS_IN_INITIALIZER_LIST(
           callback_(this,
                     &TCPClientSocketPool::ConnectingSocket::OnIOComplete)),
       pool_(pool),
+      resolver_(pool->GetHostResolver()),
       canceled_(false) {
   DCHECK(!ContainsKey(pool_->connecting_socket_map_, handle));
   pool_->connecting_socket_map_[handle] = this;
 }
 
 TCPClientSocketPool::ConnectingSocket::~ConnectingSocket() {
   if (!canceled_)
     pool_->connecting_socket_map_.erase(handle_);
 }
 
@@ skipping 92 matching lines @@
 
 void TCPClientSocketPool::ConnectingSocket::Cancel() {
   DCHECK(!canceled_);
   DCHECK(ContainsKey(pool_->connecting_socket_map_, handle_));
   pool_->connecting_socket_map_.erase(handle_);
   canceled_ = true;
 }
 
 TCPClientSocketPool::TCPClientSocketPool(
     int max_sockets_per_group,
+    HostResolver* host_resolver,
     ClientSocketFactory* client_socket_factory)
     : client_socket_factory_(client_socket_factory),
       idle_socket_count_(0),
-      max_sockets_per_group_(max_sockets_per_group) {
+      max_sockets_per_group_(max_sockets_per_group),
+      host_resolver_(host_resolver) {
 }
 
 TCPClientSocketPool::~TCPClientSocketPool() {
   // Clean up any idle sockets.  Assert that we have no remaining active
   // sockets or pending requests.  They should have all been cleaned up prior
   // to the manager being destroyed.
   CloseIdleSockets();
   DCHECK(group_map_.empty());
 }
 
@@ skipping 247 matching lines @@
 
   // Delete group if no longer needed.
   if (group.active_socket_count == 0 && group.idle_sockets.empty()) {
     DCHECK(group.pending_requests.empty());
     DCHECK(group.connecting_requests.empty());
     group_map_.erase(i);
   }
 }
 
 }  // namespace net