Add a note to avoid SSLServerSocket in new code.

net/socket/ssl_server_socket.h

 // Copyright (c) 2012 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.
+//
+// NOTE: This class is provided to support existing Chromium consumers; it is
+// NOT intended for use in NEW code. Configuring a TLS server correctly is a
+// security-sensitive activity with many subtle nuances, and thus care should be
+// taken to discuss with //net/OWNERS before any new usages.
+//
+// As such, this header should be treated as an internal implementation detail
+// of //net (where it's used for some unit test infrastructure), not as
+// appropriate for general use.
+//
+// See https://crbug.com/621176 for more details.
 
 #ifndef NET_SOCKET_SSL_SERVER_SOCKET_H_
 #define NET_SOCKET_SSL_SERVER_SOCKET_H_
 
 #include <memory>
 
 #include "net/base/completion_callback.h"
 #include "net/base/net_export.h"
 #include "net/socket/ssl_socket.h"
 #include "net/socket/stream_socket.h"
@@ skipping 50 matching lines @@
 // The |key| and |ssl_config| parameters are copied.
 //
 NET_EXPORT std::unique_ptr<SSLServerContext> CreateSSLServerContext(
     X509Certificate* certificate,
     const crypto::RSAPrivateKey& key,
     const SSLServerConfig& ssl_config);
 
 }  // namespace net
 
 #endif  // NET_SOCKET_SSL_SERVER_SOCKET_H_