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

tests/compiler/dart2js/unneeded_part_js_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.
 
 // Test that no parts are emitted when deferred loading isn't used.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'memory_source_file_helper.dart';
 
 import '../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart'
        show NullSink;
 
 import '../../../sdk/lib/_internal/compiler/compiler.dart'
        show Diagnostic;
 
 import 'dart:async';
 
 main() {
-  Uri script = currentDirectory.resolveUri(Platform.script);
+  Uri script = currentDirectory.resolve(nativeToUriPath(Platform.script));
   Uri libraryRoot = script.resolve('../../../sdk/');
   Uri packageRoot = script.resolve('./packages/');
 
   var provider = new MemorySourceFileProvider(MEMORY_SOURCE_FILES);
   void diagnosticHandler(Uri uri, int begin, int end,
                          String message, Diagnostic kind) {
     if (kind == Diagnostic.VERBOSE_INFO) {
       return;
     }
     throw '$uri:$begin:$end:$message:$kind';
@@ skipping 26 matching lines @@
 
 main() {
   var x = fisk;
   if (new DateTime.now().millisecondsSinceEpoch == 42) {
     x = new Greeting(\"I\'m confused\");
   }
   print(x.message);
 }
 """,
 };