Use SSLPrivateKey for testing client authentication

net/ssl/test_ssl_private_key.h

+// Copyright 2016 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_SSL_TEST_SSL_PLATFORM_KEY_H_
+#define NET_SSL_TEST_SSL_PLATFORM_KEY_H_
+
+#include <openssl/evp.h>
+
+#include "base/memory/ref_counted.h"
+#include "crypto/scoped_openssl_types.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+class SSLPrivateKey;
+
+// Returns a new SSLPrivateKey which uses |key| for signing operations or
+// nullptr on error.
+NET_EXPORT scoped_refptr<SSLPrivateKey> WrapOpenSSLPrivateKey(
+    crypto::ScopedEVP_PKEY key);
+
+}  // namespace net
+
+#endif  // NET_SSL_TEST_SSL_PLATFORM_KEY_H_