Revert "Remove Expect from core library."

tests/standalone/io/process_non_ascii_test.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.
 
-import "package:expect/expect.dart";
 import 'dart:io';
 import 'dart:isolate';
 
 main() {
   var port = new ReceivePort();
   var executable = new File(new Options().executable).fullPathSync();
   var tempDir = new Directory('').createTempSync();
   var nonAsciiDir = new Directory('${tempDir.path}/æøå');
   nonAsciiDir.createSync();
   var nonAsciiFile = new File('${nonAsciiDir.path}/æøå.dart');
   nonAsciiFile.writeAsStringSync(
 """
 import 'dart:io';
 
 main() {
-  if ('æøå' != new File('æøå.txt').readAsStringSync()) {
-    throw new RuntimeError("not equal");
-  }
+  Expect.equals('æøå', new File('æøå.txt').readAsStringSync());
 }
 """);
   var nonAsciiTxtFile = new File('${nonAsciiDir.path}/æøå.txt');
   nonAsciiTxtFile.writeAsStringSync('æøå');
   var options = new ProcessOptions();
   options.workingDirectory = nonAsciiDir.path;
   var script = nonAsciiFile.path;
   Process.run(executable, [script], options).then((result) {
     Expect.equals(0, result.exitCode);
     tempDir.deleteSync(recursive: true);
     port.close();
   });
 }