dart:io | Add SecureSocket.importPrivateCertificates, that reads a PKCS#12 file.

tests/standalone/io/certificate_test_client.dart

 // Copyright (c) 2013, 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.
 //
 // Client that tests that a certificate authority certificate loaded
 // at runtime can be used to verify a certificate chain. The server it
 // connects to uses localhost_cert, signed by myauthority_cert, to connect
 // securely.
 
 import 'dart:io';
@@ skipping 15 matching lines @@
   threw = false;
   try {
     SecureSocket.addCertificate(mycert, "Trust me, I'm a string");
   } on CertificateException catch (e) {
     threw = true;
   }
   if (!threw) throw new AssertException("Expected bad trust string to throw");
 
   SecureSocket.addCertificate(mycert,
                               SecureSocket.TRUST_ISSUE_SERVER_CERTIFICATES);
+
   SecureSocket.connect('localhost', port).then((SecureSocket socket) {
-    socket.writeln("hello world");
+    socket.writeln('hello world');
     socket.listen((data) { });
-    socket.close();
+    return socket.close();
+  }).then((_) {
+    SecureSocket.changeTrust('myauthority_cert', ',,');
+    return SecureSocket.connect('localhost', port);
+  }).then((_) {
+    throw new AssertException(
+        "Expected untrusted authority to stop connection");
+  }, onError: (e) {
+    if (e is! CertificateException) throw e;
+  }).then((_) {
+    SecureSocket.changeTrust('myauthority_cert', 'C,,');
+    return SecureSocket.connect('localhost', port);
+  }).then((SecureSocket socket) {
+    socket.writeln('hello world');
+    socket.listen((data) { });
+    return socket.close();
+  }).then((_) {
+    SecureSocket.removeCertificate('myauthority_cert');
+    return SecureSocket.connect('localhost', port);
+  }).then((_) {
+    throw new AssertException("Expected untrusted root to stop connection");
+  }, onError: (e) {
+    if (e is! CertificateException) throw e;
+  }).then((_) {
+    print('SUCCESS');  // Checked by parent process.
   });
 }