Make dart:io SecureSocket builtin root certificate test more robust, merge test files.

tests/standalone/io/secure_no_builtin_roots_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 "package:expect/expect.dart";
-import "dart:io";
-import "dart:isolate";
-import "dart:async";
-
-void testGoogleUrl() {
-  // We need to use an external server here because it is backed by a
-  // built-in root certificate authority.
-  InternetAddress.lookup('www.google.com').then((_) {
-    ReceivePort keepAlive = new ReceivePort();
-    HttpClient client = new HttpClient();
-    client.getUrl(Uri.parse('https://www.google.com'))
-        .then((request) => request.close())
-        .then((response) => Expect.fail("Unexpected successful connection"))
-        .catchError((error) {
-          Expect.isTrue(error is HandshakeException);
-          keepAlive.close();
-          client.close();
-        });
-  },
-  onError: (e) {
-    Expect.isTrue(e is SocketException);
-  });
-}
-
-void InitializeSSL() {
-  // If the built-in root certificates aren't loaded, the connection
-  // should signal an error.
-  SecureSocket.initialize(useBuiltinRoots: false);
-}
-
-void main() {
-  InitializeSSL();
-  testGoogleUrl();
-}