Use SecKeyCreateSignature on macOS 10.12 and later.

net/net.gypi

 # Copyright 2014 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.
 
 # This file is shared between the regular GYP build, the NaCl GYP build, and
 # the GN build. For GN support, it must have no conditionals or anything like
 # that beyond the simple one-level-deep dictionary of values.
 {
   'variables': {
     # Subset of net source files that are compiled for NaCl (net_nacl target).
@@ skipping 2133 matching lines @@
       'ssl/client_cert_store_win_unittest.cc',
       'ssl/default_channel_id_store_unittest.cc',
       'ssl/openssl_client_key_store_unittest.cc',
       'ssl/ssl_cipher_suite_names_unittest.cc',
       'ssl/ssl_client_auth_cache_unittest.cc',
       'ssl/ssl_client_session_cache_unittest.cc',
       'ssl/ssl_config_service_unittest.cc',
       'ssl/ssl_config_unittest.cc',
       'ssl/ssl_connection_status_flags_unittest.cc',
       'ssl/ssl_platform_key_android_unittest.cc',
+      'ssl/ssl_platform_key_mac_unittest.cc',
       'ssl/ssl_platform_key_util_unittest.cc',
+      'ssl/ssl_private_key_test_util.cc',
+      'ssl/ssl_private_key_test_util.h',
       'test/embedded_test_server/embedded_test_server_unittest.cc',
       'test/embedded_test_server/http_request_unittest.cc',
       'test/embedded_test_server/http_response_unittest.cc',
       'test/python_utils_unittest.cc',
       'test/run_all_unittests.cc',
       'third_party/nist-pkits/pkits_testcases-inl.h',
       'tools/content_decoder_tool/content_decoder_tool.cc',
       'tools/content_decoder_tool/content_decoder_tool.h',
       'tools/content_decoder_tool/content_decoder_tool_unittest.cc',
       'tools/quic/quic_simple_client_test.cc',
@@ skipping 1360 matching lines @@
       'third_party/nist-pkits/crls/requireExplicitPolicy5subCACRL.crl',
       'third_party/nist-pkits/crls/requireExplicitPolicy5subsubCACRL.crl',
       'third_party/nist-pkits/crls/requireExplicitPolicy5subsubsubCACRL.crl',
       'third_party/nist-pkits/crls/requireExplicitPolicy7CACRL.crl',
       'third_party/nist-pkits/crls/requireExplicitPolicy7subCARE2CRL.crl',
       'third_party/nist-pkits/crls/requireExplicitPolicy7subsubCARE2RE4CRL.crl',
       'third_party/nist-pkits/crls/requireExplicitPolicy7subsubsubCARE2RE4CRL.crl',
     ],
   }
 }