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

tests/standalone/io/process_check_arguments_script.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.
 //
 // Utility script to check that arguments are correctly passed from
 // one dart process to another using the dart:io process interface.
 import "dart:math";
 import "dart:io";
 
 class Expect {
   static void isTrue(x) {
     if (!x) {
       throw new Error("Not true");
     }
   }
 
   static void equals(x, y) {
     if (x != y) {
       throw new Error("Not equal");
     }
   }
 }
 
 main(List<String> arguments) {
-  Expect.isTrue(Platform.script.endsWith(
+  Expect.isTrue(Platform.script.path.endsWith(
       'process_check_arguments_script.dart'));
   var expected_num_args = int.parse(arguments[0]);
   var contains_quote = int.parse(arguments[1]);
   Expect.equals(expected_num_args, arguments.length);
   for (var i = 2; i < arguments.length; i++) {
     Expect.isTrue((contains_quote == 0) || arguments[i].contains('"'));
   }
 }