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

tests/standalone/io/secure_socket_bad_data_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 "dart:async";
@@ skipping 143 matching lines @@
               'received a record with an incorrect Message Authentication'));
         })
         .whenComplete(server.close);
     });
     return connectClient(server.port, hostnameInConnect).then(runClient);
   });
 }
 
 
 main() {
-  String certificateDatabase = Platform.script.resolve('pkcert').toFilePath();
+  String certificateDatabase = join(dirname(Platform.script), 'pkcert');
   SecureSocket.initialize(database: certificateDatabase,
                           password: 'dartdart',
                           useBuiltinRoots: false);
   asyncStart();
   Future.wait([test(false), test(true)])
       .then((_) => asyncEnd());
 }