Use SSLPrivateKey for testing client authentication

net/BUILD.gn

Index: net/BUILD.gn
diff --git a/net/BUILD.gn b/net/BUILD.gn
index 6203ce47bf943d91e876d8a4013ae5fff9a53bbc..8060c9a5e041712f88074edb8f96d5eb482f36ef 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -224,6 +224,8 @@ if (!is_nacl) {
       "ssl/ssl_platform_key.h",
       "ssl/ssl_platform_key_task_runner.cc",
       "ssl/ssl_platform_key_task_runner.h",
+      "ssl/test_ssl_private_key.cc",
+      "ssl/test_ssl_private_key.h",
       "ssl/threaded_ssl_private_key.cc",
       "ssl/threaded_ssl_private_key.h",
     ]
@@ -1479,7 +1481,6 @@ test("net_unittests") {
   } else {
     sources -= [
       "quic/test_tools/crypto_test_utils_openssl.cc",
-      "socket/ssl_client_socket_openssl_unittest.cc",
       "ssl/ssl_client_session_cache_openssl_unittest.cc",
     ]
   }