Add UMA for the kernel's TCP RTT estimate.

net/socket/tcp_client_socket.h

 // Copyright (c) 2011 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_SOCKET_TCP_CLIENT_SOCKET_H_
 #define NET_SOCKET_TCP_CLIENT_SOCKET_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 78 matching lines @@
 
   // Helper used by Disconnect(), which disconnects minus resetting
   // current_address_index_ and bind_address_.
   void DoDisconnect();
 
   void DidCompleteConnect(int result);
   void DidCompleteReadWrite(const CompletionCallback& callback, int result);
 
   int OpenSocket(AddressFamily family);
 
+  // Emits histograms for TCP metrics, at the time the socket is
+  // disconnected.
+  void EmitTCPMetricsHistogramsOnDisconnect();
+
   scoped_ptr<TCPSocket> socket_;
 
   // Local IP address and port we are bound to. Set to NULL if Bind()
   // wasn't called (in that case OS chooses address/port).
   scoped_ptr<IPEndPoint> bind_address_;
 
   // The list of addresses we should try in order to establish a connection.
   AddressList addresses_;
 
   // Where we are in above list. Set to -1 if uninitialized.
@@ skipping 14 matching lines @@
 
   // Failed connection attempts made while trying to connect this socket.
   ConnectionAttempts connection_attempts_;
 
   DISALLOW_COPY_AND_ASSIGN(TCPClientSocket);
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_TCP_CLIENT_SOCKET_H_