Added Socket::Close() function.

runtime/bin/socket_win.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/builtin.h"
 #include "bin/eventhandler.h"
 #include "bin/file.h"
 #include "bin/log.h"
 #include "bin/socket.h"
 
@@ skipping 255 matching lines @@
   if (status == SOCKET_ERROR) {
     DWORD rc = WSAGetLastError();
     closesocket(s);
     SetLastError(rc);
     return -1;
   }
 
   ListenSocket* listen_socket = new ListenSocket(s);
   return reinterpret_cast<intptr_t>(listen_socket);
 }
+
+
+void Socket::Close(intptr_t fd) {
+  ClientSocket* client_socket = reinterpret_cast<ClientSocket*>(fd);
+  client_socket->close();
+}