Enable client certificates in SecureSocket and SecureServerSocket

tests/standalone/io/secure_server_test.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.
 
 import "dart:io";
 import "dart:isolate";
 
 const SERVER_ADDRESS = "127.0.0.1";
 const HOST_NAME = "localhost";
 
@@ skipping 83 matching lines @@
 
 Function EndTest;
 
 const CLIENT_NAMES = const ['able', 'baker', 'camera', 'donut', 'echo'];
 
 void main() {
   ReceivePort keepAlive = new ReceivePort();
   Path scriptDir = new Path.fromNative(new Options().script).directoryPath;
   Path certificateDatabase = scriptDir.append('pkcert');
   SecureSocket.initialize(database: certificateDatabase.toNativePath(),
-                          password: 'dartdart');
+                          password: 'dartdart',
+                          useBuiltinRoots: false);
 
   var server = new SecureTestServer();
   int port = server.start();
 
   EndTest = () {
     Expect.equals(CLIENT_NAMES.length, server.numConnections);
     server.stop();
     keepAlive.close();
   };
 
   for (var x in CLIENT_NAMES) {
     new SecureTestClient(port, x);
   }
 }