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

tests/standalone/io/https_unauthorized_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 secure connections that fail due to
 // unauthenticated certificates throw exceptions in HttpClient.
 
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 import "dart:async";
 import "dart:io";
 
 const HOST_NAME = "localhost";
 const CERTIFICATE = "localhost_cert";
 
 Future<SecureServerSocket> runServer() {
   SecureSocket.initialize(
-      database: Platform.script.resolve('pkcert').toFilePath(),
+      database: join(dirname(Platform.script), 'pkcert'),
       password: 'dartdart');
 
   return HttpServer.bindSecure(
       HOST_NAME, 0, backlog: 5, certificateName: 'localhost_cert')
   .then((server) {
     server.listen((HttpRequest request) {
       request.listen((_) { }, onDone: () { request.response.close(); });
     }, onError: (e) { if (e is! HandshakeException) throw e; });
     return server;
   });
 }
 
 void main() {
-  var clientScript = Platform.script
-                             .resolve('https_unauthorized_client.dart')
-                             .toFilePath();
+  var clientScript = join(dirname(Platform.script),
+                          'https_unauthorized_client.dart');
+
   Future clientProcess(int port) {
     return Process.run(Platform.executable,
         [clientScript, port.toString()])
     .then((ProcessResult result) {
       if (result.exitCode != 0 || !result.stdout.contains('SUCCESS')) {
         print("Client failed");
         print("  stdout:");
         print(result.stdout);
         print("  stderr:");
         print(result.stderr);
         Expect.fail('Client subprocess exit code: ${result.exitCode}');
       }
     });
   }
 
   runServer().then((server) {
     clientProcess(server.port).then((_) {
       server.close();
     });
   });
 }