Compute the script Uri lazily

pkg/dev_compiler/tool/input_sdk/patch/io_patch.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.
 
 import 'dart:_js_helper' show patch;
 
 @patch
 class _Directory {
   @patch
   static _current() {
@@ skipping 237 matching lines @@
 
   @patch
   static String _version() {
     throw new UnsupportedError("Platform._version");
   }
 
   @patch
   static String _localeName() {
     throw new UnsupportedError("Platform._localeName");
   }
+
+  @patch
+  static Uri _script() {
+    throw new UnsupportedError("Platform._script");
+  }
 }
 
 @patch
 class _ProcessUtils {
   @patch
   static void _exit(int status) {
     throw new UnsupportedError("ProcessUtils._exit");
   }
 
   @patch
@@ skipping 348 matching lines @@
   }
 }
 
 @patch
 class _IOService {
   @patch
   static Future _dispatch(int request, List data) {
     throw new UnsupportedError("_IOService._dispatch");
   }
 }