Remove uses of Path class from tests/standalone.

tests/standalone/io/raw_secure_socket_test.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import "package:expect/expect.dart";
+import "package:path/path.dart";
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 
 Future<HttpServer> startServer() {
   return HttpServer.bindSecure(
       "localhost",
       0,
       backlog: 5,
       certificateName: 'localhost_cert').then((server) {
     server.listen((HttpRequest request) {
       request.listen(
         (_) { },
         onDone: () {
           request.response.contentLength = 100;
           for (int i = 0; i < 10; i++) {
             request.response.add([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
           }
           request.response.close();
         });
     });
     return server;
   });
 }
 
 void InitializeSSL() {
-  var testPkcertDatabase =
-      new Path(Platform.script).directoryPath.append('pkcert/');
-  SecureSocket.initialize(database: testPkcertDatabase.toNativePath(),
+  var testPkcertDatabase = join(dirname(Platform.script), 'pkcert');
+  SecureSocket.initialize(database: testPkcertDatabase,
                           password: 'dartdart');
 }
 
 void main() {
   List<int> message = "GET / HTTP/1.0\r\nHost: localhost\r\n\r\n".codeUnits;
   int written = 0;
   List<int> body = <int>[];
   InitializeSSL();
   startServer().then((server) {
     RawSecureSocket.connect("localhost", server.port).then((socket) {
@@ skipping 23 matching lines @@
           },
           onError: (e) {
             String msg = "onError handler of RawSecureSocket stream hit $e";
             var trace = getAttachedStackTrace(e);
             if (trace != null) msg += "\nStackTrace: $trace";
             Expect.fail(msg);
           });
     });
   });
 }