Port the remaining of dart:core to the unified corelib.

corelib/unified/core/expect.dart

 // Copyright (c) 2011, 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.
 
 /**
  * Expect is used for tests that do not want to make use of the 
  * Dart unit test library - for example, the core language tests.
  * Third parties are discouraged from using this, and should use 
  * the expect() function in the unit test library instead for 
  * test assertions.
@@ skipping 275 matching lines @@
   }
 }
 
 typedef bool _CheckExceptionFn(exception);
 
 class ExpectException implements Exception {
   ExpectException(this.message);
   String toString() => message;
   String message;
 }