Remove uses of Path class from tests/standalone.

tests/standalone/io/web_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";
 import "dart:typed_data";
 
 const String CERT_NAME = 'localhost_cert';
 const String HOST_NAME = 'localhost';
 
 /**
  * A SecurityConfiguration lets us run the tests over HTTP or HTTPS.
@@ skipping 376 matching lines @@
     testImmediateCloseClient();
     testNoUpgrade();
     testUsePOST();
     testConnections(10, 3002, "Got tired");
     testIndivitualUpgrade(5);
   }
 }
 
 
 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");
 }
 
 
 main() {
   new SecurityConfiguration(secure: false).runTests();
   initializeSSL();
   new SecurityConfiguration(secure: true).runTests();
 }