Fix two other issues, with my previous commit.

sdk/lib/io/platform_impl.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.
 
 part of dart.io;
 
 class _Platform {
   external static int _numberOfProcessors();
   external static String _pathSeparator();
   external static String _operatingSystem();
@@ skipping 10 matching lines @@
   // Cache the OS environemnt. This can be an OSError instance if
   // retrieving the environment failed.
   static var _environmentCache;
 
   static int get numberOfProcessors => _numberOfProcessors();
   static String get pathSeparator => _pathSeparator();
   static String get operatingSystem => _operatingSystem();
   static Uri script;
 
   // This script singleton is written to by the embedder if applicable.
-  static String set _nativeScript(String path) {
+  static void set _nativeScript(String path) {
     if (path.startsWith('http:') ||
         path.startsWith('https:') ||
         path.startsWith('file:')) {
       script = Uri.parse(path);
     } else {
       script = Uri.base.resolveUri(new Uri.file(path));
     }
   }
 
   static String get localHostname {
@@ skipping 65 matching lines @@
   V remove(String key) => _map.remove(key.toUpperCase());
   void clear() => _map.clear();
   void forEach(void f(String key, V value)) => _map.forEach(f);
   Iterable<String> get keys => _map.keys;
   Iterable<V> get values => _map.values;
   int get length => _map.length;
   bool get isEmpty => _map.isEmpty;
   bool get isNotEmpty => _map.isNotEmpty;
   String toString() => _map.toString();
 }