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

tests/standalone/io/https_server_test.dart

 // Copyright (c) 2012, 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.
 
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 
@@ skipping 40 matching lines @@
     });
   }
 
   // Test two servers in succession.
   test(() {
     test(() { });
   });
 }
 
 void InitializeSSL() {
-  var testPkcertDatabase = join(dirname(Platform.script), 'pkcert');
+  var testPkcertDatabase = Platform.script.resolve('pkcert').toFilePath();
   SecureSocket.initialize(database: testPkcertDatabase,
                           password: 'dartdart');
 }
 
 void main() {
   InitializeSSL();
   testListenOn();
 }