Use SecKeyCreateSignature on macOS 10.12 and later.

net/ssl/ssl_platform_key_chromecast.cc

 // 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.
 
 #include <keyhi.h>
 #include <pk11pub.h>
 #include <prerror.h>
 
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 101 matching lines @@
 
  private:
   crypto::ScopedSECKEYPrivateKey key_;
 
   DISALLOW_COPY_AND_ASSIGN(SSLPlatformKeyChromecast);
 };
 
 }  // namespace
 
 scoped_refptr<SSLPrivateKey> FetchClientCertPrivateKey(
-    X509Certificate* certificate) {
+    const X509Certificate* certificate) {
   crypto::ScopedSECKEYPrivateKey key(
       PK11_FindKeyByAnyCert(certificate->os_cert_handle(), nullptr));
   if (!key) {
     return ClientKeyStore::GetInstance()->FetchClientCertPrivateKey(
         *certificate);
   }
 
   return make_scoped_refptr(new ThreadedSSLPrivateKey(
       base::MakeUnique<SSLPlatformKeyChromecast>(std::move(key)),
       GetSSLPlatformKeyTaskRunner()));
 }
 
 }  // namespace net