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

tests/compiler/dart2js/type_promotion_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 dart2js produces the expected static type warnings for type
 // promotion langauge tests. This ensures that the analyzer and dart2js agrees
 // on these tests.
 
 import 'dart:async';
 import 'dart:io';
@@ skipping 10 matching lines @@
     'language/type_promotion_closure_test.dart',
     'language/type_promotion_functions_test.dart',
     'language/type_promotion_local_test.dart',
     'language/type_promotion_logical_and_test.dart',
     'language/type_promotion_more_specific_test.dart',
     'language/type_promotion_multiple_test.dart',
     'language/type_promotion_parameter_test.dart',
 ];
 
 void main() {
-  bool isWindows = Platform.isWindows;
-  Uri script = currentDirectory.resolveUri(Platform.script);
+  bool isWindows = (Platform.operatingSystem == 'windows');
+  Uri script = currentDirectory.resolve(nativeToUriPath(Platform.script));
   bool warningsMismatch = false;
   Future.forEach(TESTS, (String test) {
     Uri uri = script.resolve('../../$test');
     String source = UTF8.decode(readAll(uriPathToNative(uri.path)));
     SourceFile file = new StringSourceFile(
         relativize(currentDirectory, uri, isWindows), source);
     Map<int,String> expectedWarnings = {};
     int lineNo = 0;
     for (String line in source.split('\n')) {
       if (line.contains('///') && line.contains('static type warning')) {
@@ skipping 26 matching lines @@
           String line = expectedWarnings[lineNo];
           print('$uri [${lineNo+1}]: Missing static type warning.');
           print(line);
         }
       }
     });
   }).then((_) {
     Expect.isFalse(warningsMismatch);
   });
 }