Revert "Change dart:io Platform.script to return a Uri."

tests/standalone/io/secure_socket_renegotiate_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.
 
 // This test verifies that client certificates work, if the client and server
 // are in separate processes, and that connection renegotiation works, and
 // can request a client certificate to be sent.
 
 import "dart:async";
 import "dart:convert";
 import "dart:io";
 
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 
 const HOST_NAME = "localhost";
 const CERTIFICATE = "localhost_cert";
 
 
-String certificateDatabase() => Platform.script.resolve('pkcert').toFilePath();
+String certificateDatabase() => join(dirname(Platform.script), 'pkcert');
 
 
 Future<SecureServerSocket> runServer() {
   SecureSocket.initialize(database: certificateDatabase(),
                           password: 'dartdart');
 
   return SecureServerSocket.bind(HOST_NAME, 0, CERTIFICATE)
     .then((SecureServerSocket server) {
       server.listen((SecureSocket socket) {
         Expect.isNull(socket.peerCertificate);
@@ skipping 27 matching lines @@
         });
       });
       return server;
     });
 }
 
 
 void main() {
   runServer()
     .then((SecureServerSocket server) {
-      var clientScript = Platform.script
-                                 .toFilePath()
-                                 .replaceFirst("_test.dart", "_client.dart");
+      var clientScript =
+          Platform.script.replaceFirst("_test.dart", "_client.dart");
       Expect.isTrue(clientScript.endsWith("_client.dart"));
       Process.run(Platform.executable,
                   [clientScript,
                    server.port.toString(),
                    certificateDatabase()])
         .then((ProcessResult result) {
           if (result.exitCode != 0) {
             print("Client failed, stdout:");
             print(result.stdout);
             print("  stderr:");
             print(result.stderr);
             Expect.fail('Client subprocess exit code: ${result.exitCode}');
           }
         });
     });
 }