Use metadata annotation @patch for patch classes

runtime/bin/secure_socket_patch.dart

Index: runtime/bin/secure_socket_patch.dart
diff --git a/runtime/bin/secure_socket_patch.dart b/runtime/bin/secure_socket_patch.dart
index c47c9415db88ebb3bada081bd0f1b96c011e3a44..b3fde05c9f258e35b149a6a9e810955a9f19c91e 100644
--- a/runtime/bin/secure_socket_patch.dart
+++ b/runtime/bin/secure_socket_patch.dart
@@ -2,18 +2,18 @@
 // 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) =>
+@patch class SecureSocket {
+  /* @patch */ factory SecureSocket._(RawSecureSocket rawSocket) =>
       new _SecureSocket(rawSocket);
 }
 
 
-patch class _SecureFilter {
-  /* patch */ factory _SecureFilter() => new _SecureFilterImpl();
+@patch class _SecureFilter {
+  /* @patch */ factory _SecureFilter() => new _SecureFilterImpl();
 }
 
-patch class X509Certificate {
-  /* patch */ factory X509Certificate._() => new _X509CertificateImpl();
+@patch class X509Certificate {
+  /* @patch */ factory X509Certificate._() => new _X509CertificateImpl();
 }
 
 class _SecureSocket extends _Socket implements SecureSocket {
@@ -115,16 +115,16 @@ class _SecureFilterImpl
   List<_ExternalBuffer> buffers;
 }
 
-patch class SecurityContext {
-  /* patch */ factory SecurityContext() {
+@patch class SecurityContext {
+  /* @patch */ factory SecurityContext() {
     return new _SecurityContext();
   }
 
-  /* patch */ static SecurityContext get defaultContext {
+  /* @patch */ static SecurityContext get defaultContext {
     return _SecurityContext.defaultContext;
   }
 
-  /* patch */ static bool get alpnSupported {
+  /* @patch */ static bool get alpnSupported {
     return _SecurityContext.alpnSupported;
   }
 }