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

tests/standalone/io/certificate_test_client.dart

Index: tests/standalone/io/certificate_test_client.dart
diff --git a/tests/standalone/io/certificate_test_client.dart b/tests/standalone/io/certificate_test_client.dart
index f7f2fb238e0a37139cdf0d9f182541edb6b2b9ea..ff4daceeebd0f9d95eb7425f9f8b34e996f0fec9 100644
--- a/tests/standalone/io/certificate_test_client.dart
+++ b/tests/standalone/io/certificate_test_client.dart
@@ -33,9 +33,34 @@ void main() {
 
   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) { });
+    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) { });
-    socket.close();
+    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.
   });
 }