Resume testing message extraction on Windows after dart:io fix

pkg/intl/test/message_extraction/message_extraction_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.
 
 library message_extraction_test;
 
 import 'package:unittest/unittest.dart';
 import 'dart:io';
 import 'dart:async';
+import 'dart:convert';
 import 'package:path/path.dart' as path;
 import '../data_directory.dart';
 
 final dart = Platform.executable;
 
 /** The VM arguments we were given, most important package-root. */
 final vmArgs = Platform.executableArguments;
 
 /**
  * Translate a file path into this test directory, regardless of the
@@ skipping 47 matching lines @@
     print("exitCode=${previousResult.exitCode}");
   }
   var filesInTheRightDirectory = filenames.map((x) => dir(x)).toList();
   // Inject the script argument --output-dir in between the script and its
   // arguments.
   var args = []
       ..addAll(vmArgs)
       ..add(filesInTheRightDirectory.first)
       ..addAll(["--output-dir=${dir()}"])
       ..addAll(filesInTheRightDirectory.skip(1));
-  var result = Process.run(dart, args);
+  var result = Process.run(dart, args, stdoutEncoding: UTF8,
+      stderrEncoding: UTF8);
   return result;
 }
 
 Future<ProcessResult> extractMessages(ProcessResult previousResult) => run(
     previousResult,
     ['extract_to_json.dart', '--suppress-warnings', 'sample_with_messages.dart',
         'part_of_sample_with_messages.dart']);
 
 Future<ProcessResult> generateTranslationFiles(ProcessResult previousResult) =>
     run(
@@ skipping 152 matching lines @@
   verify('Null');
   verify('ein');
   verify('Mann');
   verify('Frau');
   verify('7 Mann');
   verify('7 Kanadischen dollar');
   verify('5 einige Währung oder anderen.');
   verify('1 Kanadischer dollar');
   verify('2 Kanadischen dollar');
 }