Start adding TLS (SSL) sockets to dart:io.

runtime/bin/tls_socket.dart

Index: runtime/bin/tls_socket.dart
diff --git a/runtime/bin/tls_socket.dart b/runtime/bin/tls_socket.dart
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index 0000000000000000000000000000000000000000..f3ec9ab67b6196915155709e53ef797f9a154ce0
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+// 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.
+
+interface TlsSocket extends Socket, Hashable default _TlsSocket {
+  /**
+   * Constructs a new secure socket and connect it to the given
+   * host on the given port. The returned socket is not yet connected
+   * but ready for registration of callbacks.
+   */
+  TlsSocket(String host, int port);
+}