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

tests/standalone/io/http_server_early_client_close_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";
@@ skipping 100 matching lines @@
       });
     }
   }
   runTest(tests.iterator);
 }
 
 testEarlyClose2() {
   HttpServer.bind("127.0.0.1", 0).then((server) {
     server.listen(
       (request) {
-        String name = Platform.script.toFilePath();
+        String name = Platform.script;
         new File(name).openRead().pipe(request.response)
             .catchError((e) { /* ignore */ });
       });
 
     var count = 0;
     makeRequest() {
       Socket.connect("127.0.0.1", server.port).then((socket) {
         var data = "GET / HTTP/1.1\r\nContent-Length: 0\r\n\r\n";
         socket.write(data);
         socket.close();
@@ skipping 34 matching lines @@
           socket.done.catchError((_) {});
         });
   });
 }
 
 void main() {
   testEarlyClose1();
   testEarlyClose2();
   testEarlyClose3();
 }