Move much of the TCPClientSocketPool implementation out into ClientSocketPoolBase and TCPConnectingSocket for reuse.

When I write SSLClientSocketPool, it will need to reuse lots of this functionality.  This isn't quite the interface we want yet, since we'll need a ConnectingSocket interface for both SSLConnectingSocket and TCPConnectingSocket to derive from, but this is a start.
BUG=http://crbug.com/13289
TEST=none

Review URL: http://codereview.chromium.org/118423

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18034 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 805 insertions, 501 deletions

diff --git a/net/base/client_socket_pool_base.cc b/net/base/client_socket_pool_base.cc
new file mode 100644
index 0000000..92bb28d
--- /dev/null
+++ b/net/base/client_socket_pool_base.cc
@@ -0,0 +1,342 @@
+// Copyright (c) 2009 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/client_socket_pool_base.h"
+
+#include "base/logging.h"
+#include "base/message_loop.h"
+#include "base/time.h"
+#include "base/stl_util-inl.h"
+#include "net/base/client_socket_handle.h"
+#include "net/base/net_errors.h"
+#include "net/base/tcp_connecting_socket.h"
+
+using base::TimeDelta;
+
+namespace net {
+
+namespace {
+
+// The timeout value, in seconds, used to clean up idle sockets that can't be
+// reused.
+//
+// Note: It's important to close idle sockets that have received data as soon
+// as possible because the received data may cause BSOD on Windows XP under
+// some conditions.  See http://crbug.com/4606.
+const int kCleanupInterval = 10;  // DO NOT INCREASE THIS TIMEOUT.
+
+// The maximum duration, in seconds, to keep idle persistent sockets alive.
+const int kIdleTimeout = 300;  // 5 minutes.
+
+// InsertRequestIntoQueue inserts the request into the queue based on
+// priority.  Highest priorities are closest to the front.  Older requests are
+// prioritized over requests of equal priority.
+void InsertRequestIntoQueue(
+    const ClientSocketPoolBase::Request& r,
+    ClientSocketPoolBase::RequestQueue* pending_requests) {
+  ClientSocketPoolBase::RequestQueue::iterator it = pending_requests->begin();
+  while (it != pending_requests->end() && r.priority <= it->priority)
+    ++it;
+  pending_requests->insert(it, r);
+}
+
+}  // namespace
+
+ClientSocketPoolBase::ClientSocketPoolBase(
+    int max_sockets_per_group,
+    const ConnectingSocketFactory* connecting_socket_factory)
+    : idle_socket_count_(0),
+      max_sockets_per_group_(max_sockets_per_group),
+      connecting_socket_factory_(connecting_socket_factory) {}
+
+ClientSocketPoolBase::~ClientSocketPoolBase() {
+  // 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.
+  CleanupIdleSockets(true /* force close all idle sockets */);
+  DCHECK(group_map_.empty());
+}
+
+int ClientSocketPoolBase::RequestSocket(const std::string& group_name,
+                                        const Request& request) {
+  DCHECK(!request.host.empty());
+  DCHECK_GE(request.priority, 0);
+  DCHECK(request.callback);
+  DCHECK_EQ(LOAD_STATE_IDLE, request.load_state);
+
+  Group& group = group_map_[group_name];
+
+  // Can we make another active socket now?
+  if (group.active_socket_count == max_sockets_per_group_) {
+    InsertRequestIntoQueue(request, &group.pending_requests);
+    return ERR_IO_PENDING;
+  }
+
+  // OK, we are going to activate one.
+  group.active_socket_count++;
+
+  while (!group.idle_sockets.empty()) {
+    IdleSocket idle_socket = group.idle_sockets.back();
+    group.idle_sockets.pop_back();
+    DecrementIdleCount();
+    if (idle_socket.socket->IsConnectedAndIdle()) {
+      // We found one we can reuse!
+      request.handle->set_socket(idle_socket.socket);
+      request.handle->set_is_reused(true);
+      return OK;
+    }
+    delete idle_socket.socket;
+  }
+
+  // We couldn't find a socket to reuse, so allocate and connect a new one.
+
+  // First, we need to make sure we aren't already servicing a request for this
+  // handle (which could happen if we requested, canceled, and then requested
+  // with the same handle).
+  if (ContainsKey(connecting_socket_map_, request.handle))
+    connecting_socket_map_[request.handle]->Cancel();
+
+  group.connecting_requests[request.handle] = request;
+  group.connecting_requests[request.handle].load_state =
+      LOAD_STATE_RESOLVING_HOST;
+
+  TCPConnectingSocket* connecting_socket =
+      connecting_socket_factory_->CreateConnectingSocket(group_name, request);
+  connecting_socket_map_[request.handle] = connecting_socket;
+
+  return connecting_socket->Connect();
+}
+
+void ClientSocketPoolBase::CancelRequest(const std::string& group_name,
+                                        const ClientSocketHandle* handle) {
+  DCHECK(ContainsKey(group_map_, group_name));
+
+  Group& group = group_map_[group_name];
+
+  // Search pending_requests for matching handle.
+  RequestQueue::iterator it = group.pending_requests.begin();
+  for (; it != group.pending_requests.end(); ++it) {
+    if (it->handle == handle) {
+      group.pending_requests.erase(it);
+      return;
+    }
+  }
+
+  // It's invalid to cancel a non-existent request.
+  DCHECK(ContainsKey(group.connecting_requests, handle));
+
+  RequestMap::iterator map_it = group.connecting_requests.find(handle);
+  if (map_it != group.connecting_requests.end()) {
+    group.connecting_requests.erase(map_it);
+    group.active_socket_count--;
+
+    // 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(group_name);
+    }
+  }
+}
+
+void ClientSocketPoolBase::ReleaseSocket(const std::string& group_name,
+                                        ClientSocket* socket) {
+  // Run this asynchronously to allow the caller to finish before we let
+  // another to begin doing work.  This also avoids nasty recursion issues.
+  // NOTE: We cannot refer to the handle argument after this method returns.
+  MessageLoop::current()->PostTask(FROM_HERE, NewRunnableMethod(
+      this, &ClientSocketPoolBase::DoReleaseSocket, group_name, socket));
+}
+
+int ClientSocketPoolBase::IdleSocketCountInGroup(
+    const std::string& group_name) const {
+  GroupMap::const_iterator i = group_map_.find(group_name);
+  DCHECK(i != group_map_.end());
+
+  return i->second.idle_sockets.size();
+}
+
+LoadState ClientSocketPoolBase::GetLoadState(
+    const std::string& group_name,
+    const ClientSocketHandle* handle) const {
+  DCHECK(ContainsKey(group_map_, group_name)) << group_name;
+
+  // Can't use operator[] since it is non-const.
+  const Group& group = group_map_.find(group_name)->second;
+
+  // Search connecting_requests for matching handle.
+  RequestMap::const_iterator map_it = group.connecting_requests.find(handle);
+  if (map_it != group.connecting_requests.end()) {
+    const LoadState load_state = map_it->second.load_state;
+    DCHECK(load_state == LOAD_STATE_RESOLVING_HOST ||
+           load_state == LOAD_STATE_CONNECTING);
+    return load_state;
+  }
+
+  // Search pending_requests for matching handle.
+  RequestQueue::const_iterator it = group.pending_requests.begin();
+  for (; it != group.pending_requests.end(); ++it) {
+    if (it->handle == handle) {
+      DCHECK_EQ(LOAD_STATE_IDLE, it->load_state);
+      // TODO(wtc): Add a state for being on the wait list.
+      // See http://www.crbug.com/5077.
+      return LOAD_STATE_IDLE;
+    }
+  }
+
+  NOTREACHED();
+  return LOAD_STATE_IDLE;
+}
+
+bool ClientSocketPoolBase::IdleSocket::ShouldCleanup(
+    base::TimeTicks now) const {
+  bool timed_out = (now - start_time) >=
+      base::TimeDelta::FromSeconds(kIdleTimeout);
+  return timed_out || !socket->IsConnectedAndIdle();
+}
+
+void ClientSocketPoolBase::CleanupIdleSockets(bool force) {
+  if (idle_socket_count_ == 0)
+    return;
+
+  // Current time value. Retrieving it once at the function start rather than
+  // inside the inner loop, since it shouldn't change by any meaningful amount.
+  base::TimeTicks now = base::TimeTicks::Now();
+
+  GroupMap::iterator i = group_map_.begin();
+  while (i != group_map_.end()) {
+    Group& group = i->second;
+
+    std::deque<IdleSocket>::iterator j = group.idle_sockets.begin();
+    while (j != group.idle_sockets.end()) {
+      if (force || j->ShouldCleanup(now)) {
+        delete j->socket;
+        j = group.idle_sockets.erase(j);
+        DecrementIdleCount();
+      } else {
+        ++j;
+      }
+    }
+
+    // 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++);
+    } else {
+      ++i;
+    }
+  }
+}
+
+ClientSocketPoolBase::Request* ClientSocketPoolBase::GetConnectingRequest(
+    const std::string& group_name, const ClientSocketHandle* handle) {
+  GroupMap::iterator group_it = group_map_.find(group_name);
+  if (group_it == group_map_.end())
+    return NULL;
+
+  Group& group = group_it->second;
+
+  RequestMap* request_map = &group.connecting_requests;
+  RequestMap::iterator it = request_map->find(handle);
+  if (it == request_map->end())
+    return NULL;
+
+  return &it->second;
+}
+
+CompletionCallback* ClientSocketPoolBase::OnConnectingRequestComplete(
+    const std::string& group_name,
+    const ClientSocketHandle* handle,
+    bool deactivate,
+    ClientSocket* socket) {
+  DCHECK((deactivate && !socket) || (!deactivate && socket));
+  DCHECK(ContainsKey(group_map_, group_name));
+  Group& group = group_map_[group_name];
+
+  RequestMap* request_map = &group.connecting_requests;
+
+  // TODO(willchan): For decoupling connecting sockets from requests, don't use
+  // |handle|.  Simply pop the first request from |connecting_requests|.  Handle
+  // the case where |connecting_requests| is empty by calling DoReleaseSocket().
+  DCHECK(ContainsKey(*request_map, handle));
+  RequestMap::iterator it = request_map->find(handle);
+  Request request = it->second;
+  request_map->erase(it);
+  DCHECK_EQ(request.handle, handle);
+
+  if (deactivate) {
+    group.active_socket_count--;
+
+    // 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(group_name);
+    }
+  } else {
+    request.handle->set_socket(socket);
+    request.handle->set_is_reused(false);
+  }
+
+  // TODO(willchan): Don't bother with this when decoupling connecting sockets
+  // from requests.
+  connecting_socket_map_.erase(handle);
+
+  return request.callback;
+}
+
+void ClientSocketPoolBase::IncrementIdleCount() {
+  if (++idle_socket_count_ == 1)
+    timer_.Start(TimeDelta::FromSeconds(kCleanupInterval), this,
+                 &ClientSocketPoolBase::OnCleanupTimerFired);
+}
+
+void ClientSocketPoolBase::DecrementIdleCount() {
+  if (--idle_socket_count_ == 0)
+    timer_.Stop();
+}
+
+void ClientSocketPoolBase::DoReleaseSocket(const std::string& group_name,
+                                           ClientSocket* socket) {
+  GroupMap::iterator i = group_map_.find(group_name);
+  DCHECK(i != group_map_.end());
+
+  Group& group = i->second;
+
+  DCHECK_GT(group.active_socket_count, 0);
+  group.active_socket_count--;
+
+  const bool can_reuse = socket->IsConnectedAndIdle();
+  if (can_reuse) {
+    IdleSocket idle_socket;
+    idle_socket.socket = socket;
+    idle_socket.start_time = base::TimeTicks::Now();
+
+    group.idle_sockets.push_back(idle_socket);
+    IncrementIdleCount();
+  } else {
+    delete socket;
+  }
+
+  // Process one pending request.
+  if (!group.pending_requests.empty()) {
+    Request r = group.pending_requests.front();
+    group.pending_requests.pop_front();
+
+    int rv = RequestSocket(group_name, r);
+    if (rv != ERR_IO_PENDING)
+      r.callback->Run(rv);
+    return;
+  }
+
+  // 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
diff --git a/net/base/client_socket_pool_base.h b/net/base/client_socket_pool_base.h
new file mode 100644
index 0000000..c18c5b7
--- /dev/null
+++ b/net/base/client_socket_pool_base.h
@@ -0,0 +1,177 @@
+// Copyright (c) 2009 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.
+//
+// ClientSocketPoolBase is an implementation class for building new
+// ClientSocketPools.  New ClientSocketPools should compose
+// ClientSocketPoolBase.  ClientSocketPoolBase provides functionality for
+// managing socket reuse and restricting the number of open sockets within a
+// "group".  It always returns a connected socket.  Clients of
+// ClientSocketPoolBase need to provide a ConnectingSocketFactory to generate
+// ConnectingSockets that actually perform the socket connection.
+
+#ifndef NET_BASE_CLIENT_SOCKET_POOL_BASE_H_
+#define NET_BASE_CLIENT_SOCKET_POOL_BASE_H_
+
+#include <deque>
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/ref_counted.h"
+#include "base/scoped_ptr.h"
+#include "base/task.h"
+#include "base/timer.h"
+#include "net/base/completion_callback.h"
+#include "net/base/load_states.h"
+
+namespace net {
+
+class ClientSocket;
+class ClientSocketHandle;
+class TCPConnectingSocket;
+
+// A ClientSocketPoolBase is used to restrict the number of sockets open at
+// a time.  It also maintains a list of idle persistent sockets.
+class ClientSocketPoolBase : public base::RefCounted<ClientSocketPoolBase> {
+ public:
+  // A Request is allocated per call to RequestSocket that results in
+  // ERR_IO_PENDING.
+  struct Request {
+    ClientSocketHandle* handle;
+    CompletionCallback* callback;
+    int priority;
+    std::string host;
+    int port;
+    LoadState load_state;
+  };
+
+  // Entry for a persistent socket which became idle at time |start_time|.
+  struct IdleSocket {
+    ClientSocket* socket;
+    base::TimeTicks start_time;
+
+    // An idle socket should be removed if it can't be reused, or has been idle
+    // for too long. |now| is the current time value (TimeTicks::Now()).
+    //
+    // An idle socket can't be reused if it is disconnected or has received
+    // data unexpectedly (hence no longer idle).  The unread data would be
+    // mistaken for the beginning of the next response if we were to reuse the
+    // socket for a new request.
+    bool ShouldCleanup(base::TimeTicks now) const;
+  };
+
+  typedef std::deque<Request> RequestQueue;
+  typedef std::map<const ClientSocketHandle*, Request> RequestMap;
+
+  // A Group is allocated per group_name when there are idle sockets or pending
+  // requests.  Otherwise, the Group object is removed from the map.
+  struct Group {
+    Group() : active_socket_count(0) {}
+    std::deque<IdleSocket> idle_sockets;
+    RequestQueue pending_requests;
+    RequestMap connecting_requests;
+    int active_socket_count;
+  };
+
+  typedef std::map<std::string, Group> GroupMap;
+
+  // TODO(willchan): Change the return value of CreateConnectingSocket to be
+  // ConnectingSocket*, once I've extracted out an interface for it.
+  class ConnectingSocketFactory {
+   public:
+    ConnectingSocketFactory() {}
+    virtual ~ConnectingSocketFactory() {}
+
+    // Creates a TCPConnectingSocket.  Never returns NULL.
+    virtual TCPConnectingSocket* CreateConnectingSocket(
+        const std::string& group_name, const Request& request) const = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(ConnectingSocketFactory);
+  };
+
+  ClientSocketPoolBase(
+      int max_sockets_per_group,
+      const ConnectingSocketFactory* connecting_socket_factory);
+  ~ClientSocketPoolBase();
+
+  int RequestSocket(const std::string& group_name, const Request& request);
+
+  void CancelRequest(const std::string& group_name,
+                     const ClientSocketHandle* handle);
+
+  void ReleaseSocket(const std::string& group_name, ClientSocket* socket);
+
+  int idle_socket_count() const { return idle_socket_count_; }
+
+  int IdleSocketCountInGroup(const std::string& group_name) const;
+
+  LoadState GetLoadState(const std::string& group_name,
+                         const ClientSocketHandle* handle) const;
+
+  // Closes all idle sockets if |force| is true.  Else, only closes idle
+  // sockets that timed out or can't be reused.
+  void CleanupIdleSockets(bool force);
+
+  // Used by ConnectingSocket until we remove the coupling between a specific
+  // ConnectingSocket and a ClientSocketHandle:
+
+  // Returns NULL if not found.  Otherwise it returns the Request*
+  // corresponding to the ConnectingSocket (keyed by |group_name| and |handle|.
+  // Note that this pointer may be invalidated after any call that might mutate
+  // the RequestMap or GroupMap, so the user should not hold onto the pointer
+  // for long.
+  Request* GetConnectingRequest(const std::string& group_name,
+                                const ClientSocketHandle* handle);
+
+  // Handles the completed Request corresponding to the ConnectingSocket (keyed
+  // by |group_name| and |handle|.  |deactivate| indicates whether or not to
+  // deactivate the socket, making the socket slot available for a new socket
+  // connection.  If |deactivate| is false, then set |socket| into |handle|.
+  // Returns the callback to run.
+  // TODO(willchan): When we decouple Requests and ConnectingSockets, this will
+  // return the callback of the request we select.
+  CompletionCallback* OnConnectingRequestComplete(
+      const std::string& group_name,
+      const ClientSocketHandle* handle,
+      bool deactivate,
+      ClientSocket* socket);
+
+ private:
+  // Called when the number of idle sockets changes.
+  void IncrementIdleCount();
+  void DecrementIdleCount();
+
+  // Called via PostTask by ReleaseSocket.
+  void DoReleaseSocket(const std::string& group_name, ClientSocket* socket);
+
+  // Called when timer_ fires.  This method scans the idle sockets removing
+  // sockets that timed out or can't be reused.
+  void OnCleanupTimerFired() {
+    CleanupIdleSockets(false);
+  }
+
+  GroupMap group_map_;
+
+  std::map<const ClientSocketHandle*, TCPConnectingSocket*>
+      connecting_socket_map_;
+
+  // Timer used to periodically prune idle sockets that timed out or can't be
+  // reused.
+  base::RepeatingTimer<ClientSocketPoolBase> timer_;
+
+  // The total number of idle sockets in the system.
+  int idle_socket_count_;
+
+  // The maximum number of sockets kept per group.
+  const int max_sockets_per_group_;
+
+  const ConnectingSocketFactory* const connecting_socket_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ClientSocketPoolBase);
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_CLIENT_SOCKET_POOL_BASE_H_
diff --git a/net/base/tcp_client_socket_pool.cc b/net/base/tcp_client_socket_pool.cc
index 75875f2..3f895f7 100644
--- a/net/base/tcp_client_socket_pool.cc
+++ b/net/base/tcp_client_socket_pool.cc
@@ -14,176 +14,20 @@
 #include "net/base/dns_resolution_observer.h"
 #include "net/base/net_errors.h"
 #include "net/base/tcp_client_socket.h"
+#include "net/base/tcp_connecting_socket.h"
 
 using base::TimeDelta;
 
-namespace {
-
-// The timeout value, in seconds, used to clean up idle sockets that can't be
-// reused.
-//
-// Note: It's important to close idle sockets that have received data as soon
-// as possible because the received data may cause BSOD on Windows XP under
-// some conditions.  See http://crbug.com/4606.
-const int kCleanupInterval = 10;  // DO NOT INCREASE THIS TIMEOUT.
-
-// The maximum duration, in seconds, to keep idle persistent sockets alive.
-const int kIdleTimeout = 300;  // 5 minutes.
-
-}  // namespace
-
 namespace net {
 
-TCPClientSocketPool::ConnectingSocket::ConnectingSocket(
-    const std::string& group_name,
-    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),
-      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_);
-}
-
-int TCPClientSocketPool::ConnectingSocket::Connect(
-    const std::string& host,
-    int port) {
-  DCHECK(!canceled_);
-  DidStartDnsResolution(host, this);
-  int rv = resolver_.Resolve(host, port, &addresses_, &callback_);
-  if (rv != ERR_IO_PENDING)
-    rv = OnIOCompleteInternal(rv, true /* synchronous */);
-  return rv;
-}
-
-void TCPClientSocketPool::ConnectingSocket::OnIOComplete(int result) {
-  OnIOCompleteInternal(result, false /* asynchronous */);
-}
-
-int TCPClientSocketPool::ConnectingSocket::OnIOCompleteInternal(
-    int result, bool synchronous) {
-  DCHECK_NE(result, ERR_IO_PENDING);
-
-  if (canceled_) {
-    // We got canceled, so bail out.
-    delete this;
-    return result;
-  }
-
-  GroupMap::iterator group_it = pool_->group_map_.find(group_name_);
-  if (group_it == pool_->group_map_.end()) {
-    // The request corresponding to this ConnectingSocket has been canceled.
-    // Stop bothering with it.
-    delete this;
-    return result;
-  }
-
-  Group& group = group_it->second;
-
-  RequestMap* request_map = &group.connecting_requests;
-  RequestMap::iterator it = request_map->find(handle_);
-  if (it == request_map->end()) {
-    // The request corresponding to this ConnectingSocket has been canceled.
-    // Stop bothering with it.
-    delete this;
-    return result;
-  }
-
-  if (result == OK && it->second.load_state == LOAD_STATE_RESOLVING_HOST) {
-    it->second.load_state = LOAD_STATE_CONNECTING;
-    socket_.reset(client_socket_factory_->CreateTCPClientSocket(addresses_));
-    connect_start_time_ = base::Time::Now();
-    result = socket_->Connect(&callback_);
-    if (result == ERR_IO_PENDING)
-      return result;
-  }
-
-  if (result == OK) {
-    DCHECK(connect_start_time_ != base::Time());
-    base::TimeDelta connect_duration =
-        base::Time::Now() - connect_start_time_;
-
-    UMA_HISTOGRAM_CLIPPED_TIMES(
-        FieldTrial::MakeName(
-            "Net.TCP_Connection_Latency", "DnsImpact").data(),
-        connect_duration,
-        base::TimeDelta::FromMilliseconds(1),
-        base::TimeDelta::FromMinutes(10),
-        100);
-  }
-
-  // Now, we either succeeded at Connect()'ing, or we failed at host resolution
-  // or Connect()'ing.  Either way, we'll run the callback to alert the client.
-
-  Request request = it->second;
-  request_map->erase(it);
-
-  if (result == OK) {
-    request.handle->set_socket(socket_.release());
-    request.handle->set_is_reused(false);
-  } else {
-    group.active_socket_count--;
-
-    // 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());
-      pool_->group_map_.erase(group_it);
-    }
-  }
-
-  if (!synchronous)
-    request.callback->Run(result);
-  delete this;
-  return result;
-}
-
-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,
     ClientSocketFactory* client_socket_factory)
-    : client_socket_factory_(client_socket_factory),
-      idle_socket_count_(0),
-      max_sockets_per_group_(max_sockets_per_group) {
-}
+    : base_(new ClientSocketPoolBase(max_sockets_per_group,
+                                     &connecting_socket_factory_)),
+      connecting_socket_factory_(base_, client_socket_factory) {}
 
-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());
-}
-
-// InsertRequestIntoQueue inserts the request into the queue based on
-// priority.  Highest priorities are closest to the front.  Older requests are
-// prioritized over requests of equal priority.
-//
-// static
-void TCPClientSocketPool::InsertRequestIntoQueue(
-    const Request& r, RequestQueue* pending_requests) {
-  RequestQueue::iterator it = pending_requests->begin();
-  while (it != pending_requests->end() && r.priority <= it->priority)
-    ++it;
-  pending_requests->insert(it, r);
-}
+TCPClientSocketPool::~TCPClientSocketPool() {}
 
 int TCPClientSocketPool::RequestSocket(const std::string& group_name,
                                        const std::string& host,
@@ -191,241 +35,61 @@ int TCPClientSocketPool::RequestSocket(const std::string& group_name,
                                        int priority,
                                        ClientSocketHandle* handle,
                                        CompletionCallback* callback) {
-  DCHECK(!host.empty());
-  DCHECK_GE(priority, 0);
-  Group& group = group_map_[group_name];
-
-  // Can we make another active socket now?
-  if (group.active_socket_count == max_sockets_per_group_) {
-    Request r;
-    r.handle = handle;
-    DCHECK(callback);
-    r.callback = callback;
-    r.priority = priority;
-    r.host = host;
-    r.port = port;
-    r.load_state = LOAD_STATE_IDLE;
-    InsertRequestIntoQueue(r, &group.pending_requests);
-    return ERR_IO_PENDING;
-  }
-
-  // OK, we are going to activate one.
-  group.active_socket_count++;
-
-  while (!group.idle_sockets.empty()) {
-    IdleSocket idle_socket = group.idle_sockets.back();
-    group.idle_sockets.pop_back();
-    DecrementIdleCount();
-    if (idle_socket.socket->IsConnectedAndIdle()) {
-      // We found one we can reuse!
-      handle->set_socket(idle_socket.socket);
-      handle->set_is_reused(true);
-      return OK;
-    }
-    delete idle_socket.socket;
-  }
-
-  // We couldn't find a socket to reuse, so allocate and connect a new one.
-
-  // First, we need to make sure we aren't already servicing a request for this
-  // handle (which could happen if we requested, canceled, and then requested
-  // with the same handle).
-  if (ContainsKey(connecting_socket_map_, handle))
-    connecting_socket_map_[handle]->Cancel();
-
-  Request r;
-  r.handle = handle;
-  DCHECK(callback);
-  r.callback = callback;
-  r.priority = priority;
-  r.host = host;
-  r.port = port;
-  r.load_state = LOAD_STATE_RESOLVING_HOST;
-  group_map_[group_name].connecting_requests[handle] = r;
-
-  // connecting_socket will delete itself.
-  ConnectingSocket* connecting_socket =
-      new ConnectingSocket(group_name, handle, client_socket_factory_, this);
-  int rv = connecting_socket->Connect(host, port);
-  return rv;
+  ClientSocketPoolBase::Request request;
+  request.host = host;
+  request.port = port;
+  request.priority = priority;
+  request.handle = handle;
+  request.callback = callback;
+  request.load_state = LOAD_STATE_IDLE;
+  return base_->RequestSocket(group_name, request);
 }
 
 void TCPClientSocketPool::CancelRequest(const std::string& group_name,
                                         const ClientSocketHandle* handle) {
-  DCHECK(ContainsKey(group_map_, group_name));
-
-  Group& group = group_map_[group_name];
-
-  // Search pending_requests for matching handle.
-  RequestQueue::iterator it = group.pending_requests.begin();
-  for (; it != group.pending_requests.end(); ++it) {
-    if (it->handle == handle) {
-      group.pending_requests.erase(it);
-      return;
-    }
-  }
-
-  // It's invalid to cancel a non-existent request.
-  DCHECK(ContainsKey(group.connecting_requests, handle));
-
-  RequestMap::iterator map_it = group.connecting_requests.find(handle);
-  if (map_it != group.connecting_requests.end()) {
-    group.connecting_requests.erase(map_it);
-    group.active_socket_count--;
-
-    // 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(group_name);
-    }
-  }
+  base_->CancelRequest(group_name, handle);
 }
 
 void TCPClientSocketPool::ReleaseSocket(const std::string& group_name,
                                         ClientSocket* socket) {
-  // Run this asynchronously to allow the caller to finish before we let
-  // another to begin doing work.  This also avoids nasty recursion issues.
-  // NOTE: We cannot refer to the handle argument after this method returns.
-  MessageLoop::current()->PostTask(FROM_HERE, NewRunnableMethod(
-      this, &TCPClientSocketPool::DoReleaseSocket, group_name, socket));
+  base_->ReleaseSocket(group_name, socket);
 }
 
 void TCPClientSocketPool::CloseIdleSockets() {
-  CleanupIdleSockets(true);
+  base_->CleanupIdleSockets(true);
 }
 
 int TCPClientSocketPool::IdleSocketCountInGroup(
     const std::string& group_name) const {
-  GroupMap::const_iterator i = group_map_.find(group_name);
-  DCHECK(i != group_map_.end());
-
-  return i->second.idle_sockets.size();
+  return base_->IdleSocketCountInGroup(group_name);
 }
 
 LoadState TCPClientSocketPool::GetLoadState(
     const std::string& group_name,
     const ClientSocketHandle* handle) const {
-  DCHECK(ContainsKey(group_map_, group_name)) << group_name;
-
-  // Can't use operator[] since it is non-const.
-  const Group& group = group_map_.find(group_name)->second;
-
-  // Search connecting_requests for matching handle.
-  RequestMap::const_iterator map_it = group.connecting_requests.find(handle);
-  if (map_it != group.connecting_requests.end()) {
-    const LoadState load_state = map_it->second.load_state;
-    DCHECK(load_state == LOAD_STATE_RESOLVING_HOST ||
-           load_state == LOAD_STATE_CONNECTING);
-    return load_state;
-  }
-
-  // Search pending_requests for matching handle.
-  RequestQueue::const_iterator it = group.pending_requests.begin();
-  for (; it != group.pending_requests.end(); ++it) {
-    if (it->handle == handle) {
-      DCHECK_EQ(LOAD_STATE_IDLE, it->load_state);
-      // TODO(wtc): Add a state for being on the wait list.
-      // See http://www.crbug.com/5077.
-      return LOAD_STATE_IDLE;
-    }
-  }
-
-  NOTREACHED();
-  return LOAD_STATE_IDLE;
-}
-
-bool TCPClientSocketPool::IdleSocket::ShouldCleanup(base::TimeTicks now) const {
-  bool timed_out = (now - start_time) >=
-      base::TimeDelta::FromSeconds(kIdleTimeout);
-  return timed_out || !socket->IsConnectedAndIdle();
+  return base_->GetLoadState(group_name, handle);
 }
 
-void TCPClientSocketPool::CleanupIdleSockets(bool force) {
-  if (idle_socket_count_ == 0)
-    return;
-
-  // Current time value. Retrieving it once at the function start rather than
-  // inside the inner loop, since it shouldn't change by any meaningful amount.
-  base::TimeTicks now = base::TimeTicks::Now();
-
-  GroupMap::iterator i = group_map_.begin();
-  while (i != group_map_.end()) {
-    Group& group = i->second;
-
-    std::deque<IdleSocket>::iterator j = group.idle_sockets.begin();
-    while (j != group.idle_sockets.end()) {
-      if (force || j->ShouldCleanup(now)) {
-        delete j->socket;
-        j = group.idle_sockets.erase(j);
-        DecrementIdleCount();
-      } else {
-        ++j;
-      }
-    }
-
-    // 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++);
-    } else {
-      ++i;
-    }
-  }
-}
-
-void TCPClientSocketPool::IncrementIdleCount() {
-  if (++idle_socket_count_ == 1)
-    timer_.Start(TimeDelta::FromSeconds(kCleanupInterval), this,
-                 &TCPClientSocketPool::OnCleanupTimerFired);
-}
+TCPClientSocketPool::TCPConnectingSocketFactory::TCPConnectingSocketFactory(
+    const scoped_refptr<ClientSocketPoolBase>& base,
+    ClientSocketFactory* client_socket_factory)
+    : base_(base),
+      client_socket_factory_(client_socket_factory) {}
 
-void TCPClientSocketPool::DecrementIdleCount() {
-  if (--idle_socket_count_ == 0)
-    timer_.Stop();
+TCPClientSocketPool::TCPConnectingSocketFactory::~TCPConnectingSocketFactory() {
 }
 
-void TCPClientSocketPool::DoReleaseSocket(const std::string& group_name,
-                                          ClientSocket* socket) {
-  GroupMap::iterator i = group_map_.find(group_name);
-  DCHECK(i != group_map_.end());
-
-  Group& group = i->second;
-
-  DCHECK_GT(group.active_socket_count, 0);
-  group.active_socket_count--;
-
-  const bool can_reuse = socket->IsConnectedAndIdle();
-  if (can_reuse) {
-    IdleSocket idle_socket;
-    idle_socket.socket = socket;
-    idle_socket.start_time = base::TimeTicks::Now();
-
-    group.idle_sockets.push_back(idle_socket);
-    IncrementIdleCount();
-  } else {
-    delete socket;
-  }
-
-  // Process one pending request.
-  if (!group.pending_requests.empty()) {
-    Request r = group.pending_requests.front();
-    group.pending_requests.pop_front();
-
-    int rv = RequestSocket(
-        group_name, r.host, r.port, r.priority, r.handle, r.callback);
-    if (rv != ERR_IO_PENDING)
-      r.callback->Run(rv);
-    return;
-  }
-
-  // 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);
-  }
+TCPConnectingSocket*
+TCPClientSocketPool::TCPConnectingSocketFactory::CreateConnectingSocket(
+    const std::string& group_name,
+    const ClientSocketPoolBase::Request& request) const {
+  return new TCPConnectingSocket(group_name,
+                                 request.host,
+                                 request.port,
+                                 request.handle,
+                                 request.callback,
+                                 client_socket_factory_,
+                                 base_);
 }
 
 }  // namespace net
diff --git a/net/base/tcp_client_socket_pool.h b/net/base/tcp_client_socket_pool.h
index 8d4a3bd..c92a081 100644
--- a/net/base/tcp_client_socket_pool.h
+++ b/net/base/tcp_client_socket_pool.h
@@ -5,19 +5,15 @@
 #ifndef NET_BASE_TCP_CLIENT_SOCKET_POOL_H_
 #define NET_BASE_TCP_CLIENT_SOCKET_POOL_H_
 
-#include <deque>
-#include <map>
 #include <string>
 
-#include "base/scoped_ptr.h"
-#include "base/timer.h"
-#include "net/base/address_list.h"
 #include "net/base/client_socket_pool.h"
-#include "net/base/host_resolver.h"
+#include "net/base/client_socket_pool_base.h"
 
 namespace net {
 
 class ClientSocketFactory;
+class TCPConnectingSocket;
 
 // A TCPClientSocketPool is used to restrict the number of TCP sockets open at
 // a time.  It also maintains a list of idle persistent sockets.
@@ -44,9 +40,7 @@ class TCPClientSocketPool : public ClientSocketPool {
 
   virtual void CloseIdleSockets();
 
-  virtual int idle_socket_count() const {
-    return idle_socket_count_;
-  }
+  virtual int idle_socket_count() const { return base_->idle_socket_count(); }
 
   virtual int IdleSocketCountInGroup(const std::string& group_name) const;
 
@@ -54,136 +48,29 @@ class TCPClientSocketPool : public ClientSocketPool {
                                  const ClientSocketHandle* handle) const;
 
  private:
-  // A Request is allocated per call to RequestSocket that results in
-  // ERR_IO_PENDING.
-  struct Request {
-    ClientSocketHandle* handle;
-    CompletionCallback* callback;
-    int priority;
-    std::string host;
-    int port;
-    LoadState load_state;
-  };
-
-  // Entry for a persistent socket which became idle at time |start_time|.
-  struct IdleSocket {
-    ClientSocket* socket;
-    base::TimeTicks start_time;
-
-    // An idle socket should be removed if it can't be reused, or has been idle
-    // for too long. |now| is the current time value (TimeTicks::Now()).
-    //
-    // An idle socket can't be reused if it is disconnected or has received
-    // data unexpectedly (hence no longer idle).  The unread data would be
-    // mistaken for the beginning of the next response if we were to reuse the
-    // socket for a new request.
-    bool ShouldCleanup(base::TimeTicks now) const;
-  };
-
-  typedef std::deque<Request> RequestQueue;
-  typedef std::map<const ClientSocketHandle*, Request> RequestMap;
-
-  // A Group is allocated per group_name when there are idle sockets or pending
-  // requests.  Otherwise, the Group object is removed from the map.
-  struct Group {
-    Group() : active_socket_count(0) {}
-    std::deque<IdleSocket> idle_sockets;
-    RequestQueue pending_requests;
-    RequestMap connecting_requests;
-    int active_socket_count;
-  };
-
-  typedef std::map<std::string, Group> GroupMap;
-
-  // ConnectingSocket handles the host resolution necessary for socket creation
-  // and the Connect().
-  class ConnectingSocket {
+  class TCPConnectingSocketFactory
+      : public ClientSocketPoolBase::ConnectingSocketFactory {
    public:
-    enum State {
-      STATE_RESOLVE_HOST,
-      STATE_CONNECT
-    };
-
-    ConnectingSocket(const std::string& group_name,
-                     const ClientSocketHandle* handle,
-                     ClientSocketFactory* client_socket_factory,
-                     TCPClientSocketPool* pool);
-    ~ConnectingSocket();
-
-    // Begins the host resolution and the TCP connect.  Returns OK on success
-    // and ERR_IO_PENDING if it cannot immediately service the request.
-    // Otherwise, it returns a net error code.
-    int Connect(const std::string& host, int port);
-
-    // Called by the TCPClientSocketPool to cancel this ConnectingSocket.  Only
-    // necessary if a ClientSocketHandle is reused.
-    void Cancel();
+    TCPConnectingSocketFactory(
+        const scoped_refptr<ClientSocketPoolBase>& base,
+        ClientSocketFactory* factory);
+    virtual ~TCPConnectingSocketFactory();
+
+    virtual TCPConnectingSocket* CreateConnectingSocket(
+        const std::string& group_name,
+        const ClientSocketPoolBase::Request& request) const;
 
    private:
-    // Handles asynchronous completion of IO.  |result| represents the result of
-    // the IO operation.
-    void OnIOComplete(int result);
-
-    // Handles both asynchronous and synchronous completion of IO.  |result|
-    // represents the result of the IO operation.  |synchronous| indicates
-    // whether or not the previous IO operation completed synchronously or
-    // asynchronously.  OnIOCompleteInternal returns the result of the next IO
-    // operation that executes, or just the value of |result|.
-    int OnIOCompleteInternal(int result, bool synchronous);
-
-    const std::string group_name_;
-    const ClientSocketHandle* const handle_;
+    const scoped_refptr<ClientSocketPoolBase> base_;
     ClientSocketFactory* const client_socket_factory_;
-    CompletionCallbackImpl<ConnectingSocket> callback_;
-    scoped_ptr<ClientSocket> socket_;
-    scoped_refptr<TCPClientSocketPool> pool_;
-    HostResolver resolver_;
-    AddressList addresses_;
-    bool canceled_;
 
-    // The time the Connect() method was called (if it got called).
-    base::Time connect_start_time_;
-
-    DISALLOW_COPY_AND_ASSIGN(ConnectingSocket);
+    DISALLOW_COPY_AND_ASSIGN(TCPConnectingSocketFactory);
   };
 
   virtual ~TCPClientSocketPool();
 
-  static void InsertRequestIntoQueue(const Request& r,
-                                     RequestQueue* pending_requests);
-
-  // Closes all idle sockets if |force| is true.  Else, only closes idle
-  // sockets that timed out or can't be reused.
-  void CleanupIdleSockets(bool force);
-
-  // Called when the number of idle sockets changes.
-  void IncrementIdleCount();
-  void DecrementIdleCount();
-
-  // Called via PostTask by ReleaseSocket.
-  void DoReleaseSocket(const std::string& group_name, ClientSocket* socket);
-
-  // Called when timer_ fires.  This method scans the idle sockets removing
-  // sockets that timed out or can't be reused.
-  void OnCleanupTimerFired() {
-    CleanupIdleSockets(false);
-  }
-
-  ClientSocketFactory* const client_socket_factory_;
-
-  GroupMap group_map_;
-
-  std::map<const ClientSocketHandle*, ConnectingSocket*> connecting_socket_map_;
-
-  // Timer used to periodically prune idle sockets that timed out or can't be
-  // reused.
-  base::RepeatingTimer<TCPClientSocketPool> timer_;
-
-  // The total number of idle sockets in the system.
-  int idle_socket_count_;
-
-  // The maximum number of sockets kept per group.
-  const int max_sockets_per_group_;
+  const scoped_refptr<ClientSocketPoolBase> base_;
+  const TCPConnectingSocketFactory connecting_socket_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(TCPClientSocketPool);
 };
diff --git a/net/base/tcp_connecting_socket.cc b/net/base/tcp_connecting_socket.cc
new file mode 100644
index 0000000..82e1952
--- /dev/null
+++ b/net/base/tcp_connecting_socket.cc
@@ -0,0 +1,150 @@
+// 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_connecting_socket.h"
+
+#include "base/compiler_specific.h"
+#include "base/field_trial.h"
+#include "base/stl_util-inl.h"
+#include "base/time.h"
+#include "net/base/client_socket_factory.h"
+#include "net/base/client_socket_handle.h"
+#include "net/base/client_socket_pool_base.h"
+#include "net/base/dns_resolution_observer.h"
+#include "net/base/net_errors.h"
+#include "net/base/tcp_client_socket.h"
+
+using base::TimeDelta;
+
+namespace {
+
+// The timeout value, in seconds, used to clean up idle sockets that can't be
+// reused.
+//
+// Note: It's important to close idle sockets that have received data as soon
+// as possible because the received data may cause BSOD on Windows XP under
+// some conditions.  See http://crbug.com/4606.
+const int kCleanupInterval = 10;  // DO NOT INCREASE THIS TIMEOUT.
+
+// The maximum duration, in seconds, to keep idle persistent sockets alive.
+const int kIdleTimeout = 300;  // 5 minutes.
+
+}  // namespace
+
+namespace net {
+
+TCPConnectingSocket::TCPConnectingSocket(
+    const std::string& group_name,
+    const std::string& host,
+    int port,
+    const ClientSocketHandle* handle,
+    CompletionCallback* callback,
+    ClientSocketFactory* client_socket_factory,
+    const scoped_refptr<ClientSocketPoolBase>& pool)
+    : group_name_(group_name),
+      host_(host),
+      port_(port),
+      handle_(handle),
+      user_callback_(callback),
+      client_socket_factory_(client_socket_factory),
+      ALLOW_THIS_IN_INITIALIZER_LIST(
+          callback_(this,
+                    &TCPConnectingSocket::OnIOComplete)),
+      pool_(pool),
+      canceled_(false) {}
+
+TCPConnectingSocket::~TCPConnectingSocket() {}
+
+int TCPConnectingSocket::Connect() {
+  DCHECK(!canceled_);
+  DidStartDnsResolution(host_, this);
+  int rv = resolver_.Resolve(host_, port_, &addresses_, &callback_);
+  if (rv == OK) {
+    rv = OnIOCompleteInternal(rv, true /* synchronous */);
+  }
+  return rv;
+}
+
+void TCPConnectingSocket::OnIOComplete(int result) {
+  OnIOCompleteInternal(result, false /* asynchronous */);
+}
+
+int TCPConnectingSocket::OnIOCompleteInternal(int result, bool synchronous) {
+  DCHECK_NE(result, ERR_IO_PENDING);
+
+  if (canceled_) {
+    // We got canceled, so bail out.
+    delete this;
+    return result;
+  }
+
+  ClientSocketPoolBase::Request* request = pool_->GetConnectingRequest(
+      group_name_, handle_);
+  if (!request) {
+    // The request corresponding to this TCPConnectingSocket has been canceled.
+    // Stop bothering with it.
+    delete this;
+    return result;
+  }
+
+  if (result == OK && request->load_state == LOAD_STATE_RESOLVING_HOST) {
+    request->load_state = LOAD_STATE_CONNECTING;
+    socket_.reset(client_socket_factory_->CreateTCPClientSocket(addresses_));
+    connect_start_time_ = base::Time::Now();
+    result = socket_->Connect(&callback_);
+    if (result == ERR_IO_PENDING)
+      return result;
+  }
+
+  if (result == OK) {
+    DCHECK_EQ(request->load_state, LOAD_STATE_CONNECTING);
+    DCHECK(connect_start_time_ != base::Time());
+    base::TimeDelta connect_duration =
+        base::Time::Now() - connect_start_time_;
+
+    UMA_HISTOGRAM_CLIPPED_TIMES(
+        FieldTrial::MakeName(
+            "Net.TCP_Connection_Latency", "DnsImpact").data(),
+        connect_duration,
+        base::TimeDelta::FromMilliseconds(1),
+        base::TimeDelta::FromMinutes(10),
+        100);
+  }
+
+  // Now, we either succeeded at Connect()'ing, or we failed at host resolution
+  // or Connect()'ing.  Either way, we'll run the callback to alert the client.
+
+  CompletionCallback* callback = NULL;
+
+  if (result == OK) {
+    callback = pool_->OnConnectingRequestComplete(
+        group_name_,
+        handle_,
+        false /* don't deactivate socket */,
+        socket_.release());
+  } else {
+    callback = pool_->OnConnectingRequestComplete(
+        group_name_,
+        handle_,
+        true /* deactivate socket */,
+        NULL /* no socket to give */);
+  }
+
+  // TODO(willchan): Eventually this DCHECK will not be true, once we timeout
+  // slow connecting sockets and allocate extra connecting sockets to avoid the
+  // 3s timeout.
+  DCHECK(callback);
+
+  if (!synchronous)
+    callback->Run(result);
+  delete this;
+  return result;
+}
+
+void TCPConnectingSocket::Cancel() {
+  DCHECK(!canceled_);
+  canceled_ = true;
+}
+
+}  // namespace net
diff --git a/net/base/tcp_connecting_socket.h b/net/base/tcp_connecting_socket.h
new file mode 100644
index 0000000..7096692
--- /dev/null
+++ b/net/base/tcp_connecting_socket.h
@@ -0,0 +1,80 @@
+// 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.
+
+#ifndef NET_BASE_TCP_CONNECTING_SOCKET_H_
+#define NET_BASE_TCP_CONNECTING_SOCKET_H_
+
+#include <deque>
+#include <map>
+#include <string>
+
+#include "base/scoped_ptr.h"
+#include "base/timer.h"
+#include "net/base/address_list.h"
+#include "net/base/client_socket_pool.h"
+#include "net/base/host_resolver.h"
+
+namespace net {
+
+class ClientSocketFactory;
+class ClientSocketPoolBase;
+
+// TCPConnectingSocket handles host resolution and socket connection for a TCP
+// socket.
+class TCPConnectingSocket {
+ public:
+  TCPConnectingSocket(const std::string& group_name,
+                      const std::string& host,
+                      int port,
+                      const ClientSocketHandle* handle,
+                      CompletionCallback* callback,
+                      ClientSocketFactory* client_socket_factory,
+                      const scoped_refptr<ClientSocketPoolBase>& pool);
+  ~TCPConnectingSocket();
+
+  // Begins the host resolution and the TCP connect.  Returns OK on success
+  // and ERR_IO_PENDING if it cannot immediately service the request.
+  // Otherwise, it returns a net error code.
+  int Connect();
+
+  // TODO(willchan): Delete this function once we decouple connecting sockets
+  // from requests, since we'll keep around the idle connected socket.
+  // Called by the ClientSocketPoolBase to cancel this TCPConnectingSocket.
+  // Only necessary if a ClientSocketHandle is reused.
+  void Cancel();
+
+ private:
+  // Handles asynchronous completion of IO.  |result| represents the result of
+  // the IO operation.
+  void OnIOComplete(int result);
+
+  // Handles both asynchronous and synchronous completion of IO.  |result|
+  // represents the result of the IO operation.  |synchronous| indicates
+  // whether or not the previous IO operation completed synchronously or
+  // asynchronously.  OnIOCompleteInternal returns the result of the next IO
+  // operation that executes, or just the value of |result|.
+  int OnIOCompleteInternal(int result, bool synchronous);
+
+  const std::string group_name_;
+  const std::string host_;
+  const int port_;
+  const ClientSocketHandle* const handle_;
+  CompletionCallback* const user_callback_;
+  ClientSocketFactory* const client_socket_factory_;
+  CompletionCallbackImpl<TCPConnectingSocket> callback_;
+  scoped_ptr<ClientSocket> socket_;
+  const scoped_refptr<ClientSocketPoolBase> pool_;
+  HostResolver resolver_;
+  AddressList addresses_;
+  bool canceled_;
+
+  // The time the Connect() method was called (if it got called).
+  base::Time connect_start_time_;
+
+  DISALLOW_COPY_AND_ASSIGN(TCPConnectingSocket);
+};
+
+}  // namespace net
+
+#endif  // NET_BASE_TCP_CONNECTING_SOCKET_H_
diff --git a/net/net.gyp b/net/net.gyp
index 37bc3a7..66f888d 100644
--- a/net/net.gyp
+++ b/net/net.gyp
@@ -50,6 +50,8 @@
         'base/client_socket_handle.cc',
         'base/client_socket_handle.h',
         'base/client_socket_pool.h',
+        'base/client_socket_pool_base.cc',
+        'base/client_socket_pool_base.h',
         'base/completion_callback.h',
         'base/connection_type_histograms.cc',
         'base/connection_type_histograms.h',
@@ -130,6 +132,8 @@
         'base/tcp_client_socket_pool.h',
         'base/tcp_client_socket_win.cc',
         'base/tcp_client_socket_win.h',
+        'base/tcp_connecting_socket.cc',
+        'base/tcp_connecting_socket.h',
         'base/telnet_server.cc',
         'base/telnet_server.h',
         'base/upload_data.cc',