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

tests/standalone/io/secure_builtin_roots_database_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 "package:path/path.dart";
-import "dart:io";
-import "dart:isolate";
-import "dart:async";
-
-void testGoogleUrl() {
-  ReceivePort keepAlive = new ReceivePort();
-  HttpClient client = new HttpClient();
-  client.getUrl(Uri.parse('https://www.google.com'))
-      .then((request) => request.close())
-      .then((response)=> response.last)
-      .then((_) {
-        client.close();
-        keepAlive.close();
-      });
-}
-
-void InitializeSSL() {
-  // If the built-in root certificates aren't loaded, the connection
-  // should signal an error.  Even when an external database is loaded,
-  // they should not be loaded.
-  var certificateDatabase = join(dirname(Platform.script), 'pkcert');
-  SecureSocket.initialize(database: certificateDatabase,
-                          password: 'dartdart',
-                          useBuiltinRoots: true);
-}
-
-void main() {
-  InitializeSSL();
-  testGoogleUrl();
-}