Implements secure sockets on Mac OS with SecureTransport API

runtime/bin/secure_socket_patch.dart

 // 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.
 
 patch class SecureSocket {
   /* patch */ factory SecureSocket._(RawSecureSocket rawSocket) =>
       new _SecureSocket(rawSocket);
 }
 
 
@@ skipping 105 matching lines @@
 }
 
 patch class SecurityContext {
   /* patch */ factory SecurityContext() {
     return new _SecurityContext();
   }
 
   /* patch */ static SecurityContext get defaultContext {
     return _SecurityContext.defaultContext;
   }
+
+  /* patch */ static bool get alpnSupported {
+    return _SecurityContext.alpnSupported;
+  }
 }
 
 class _SecurityContext
     extends NativeFieldWrapperClass1
     implements SecurityContext {
   _SecurityContext() {
     _createNativeContext();
   }
 
   void _createNativeContext() native "SecurityContext_Allocate";
@@ skipping 22 matching lines @@
   void useCertificateChainBytes(List<int> chainBytes, {String password})
       native "SecurityContext_UseCertificateChainBytes";
 
   void setClientAuthorities(String file, {String password}) {
     List<int> bytes = (new File(file)).readAsBytesSync();
     setClientAuthoritiesBytes(bytes, password: password);
   }
   void setClientAuthoritiesBytes(List<int> authCertBytes, {String password})
       native "SecurityContext_SetClientAuthoritiesBytes";
 
+  static bool get alpnSupported => _alpnSupported();
+  static bool _alpnSupported() native "SecurityContext_AlpnSupported";
   void setAlpnProtocols(List<String> protocols, bool isServer) {
     Uint8List encodedProtocols =
         SecurityContext._protocolsToLengthEncoding(protocols);
     _setAlpnProtocols(encodedProtocols, isServer);
   }
   void _setAlpnProtocols(Uint8List protocols, bool isServer)
       native "SecurityContext_SetAlpnProtocols";
   void _trustBuiltinRoots()
       native "SecurityContext_TrustBuiltinRoots";
 }
@@ skipping 14 matching lines @@
     return new DateTime.fromMillisecondsSinceEpoch(_startValidity(),
                                                    isUtc: true);
   }
   DateTime get endValidity {
     return new DateTime.fromMillisecondsSinceEpoch(_endValidity(),
                                                    isUtc: true);
   }
   int _startValidity() native "X509_StartValidity";
   int _endValidity() native "X509_EndValidity";
 }