Implements secure sockets on Mac OS with SecureTransport API

runtime/bin/secure_socket_boringssl.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#ifndef BIN_SECURE_SOCKET_H_
-#define BIN_SECURE_SOCKET_H_
+#ifndef BIN_SECURE_SOCKET_BORINGSSL_H_
+#define BIN_SECURE_SOCKET_BORINGSSL_H_
 
-#ifdef DART_IO_SECURE_SOCKET_DISABLED
-#error "secure_socket.h can only be included on builds with SSL enabled"
+#if !defined(BIN_SECURE_SOCKET_H_)
+#error Do not include secure_socket_boringssl.h directly. Use secure_socket.h.
 #endif
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 
 #include <openssl/bio.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
@@ skipping 103 matching lines @@
   }
   Dart_Handle InitializeBuffers(Dart_Handle dart_this);
   void InitializePlatformData();
 
   DISALLOW_COPY_AND_ASSIGN(SSLFilter);
 };
 
 }  // namespace bin
 }  // namespace dart
 
-#endif  // BIN_SECURE_SOCKET_H_
+#endif  // BIN_SECURE_SOCKET_BORINGSSL_H_