Revert "Remove Expect from core library."

tests/standalone/io/skipping_dart2js_compilations_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.
 
 /*
  * This test makes sure that the "skipping Dart2Js compilations if the output is
  * already up to date" feature does work as it should.
  * Therefore this test ensures that compilations are only skipped if the last
  * modified date of the output of a dart2js compilation is newer than
  *   - the the dart application to compile (including it's dependencies)
  *   - the dart2js snapshot
  * Furtheremore it ensure that a compilations is not skipped if any of the
  * necessary files could not be found (dart2js snapshots, previous dart2js
  * output (+deps file), dart application)
  */
 
-import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:io';
 import 'dart:uri';
 import '../../../tools/testing/dart/test_suite.dart' as suite;
 import '../../../tools/testing/dart/test_runner.dart' as runner;
 import '../../../tools/testing/dart/test_options.dart' as options;
 import '../../../tools/testing/dart/status_file_parser.dart' as status;
 
 /**
  * This class is reponsible for setting up the files necessary for this test
@@ skipping 213 matching lines @@
       cleanup();
       throw error;
     }).then((_) {
       cleanup();
     });
   }
   // We need to wait some time to make sure that the files we 'touch' get a
   // bigger timestamp than the old ones
   new Timer(new Duration(seconds: 1), touchFilesAndRunTests);
 }