Revert "Remove Expect from core library."

tests/standalone/byte_array_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.
 //
 // Dart test program for testing native byte arrays.
 
 // Library tag to be able to run in html test framework.
 library ByteArrayTest;
 
-import "package:expect/expect.dart";
 import 'dart:scalarlist';
 
 void testCreateUint8ByteArray() {
   Uint8List byteArray;
 
   byteArray = new Uint8List(0);
   Expect.isTrue(byteArray is Uint8List);
   Expect.isFalse(byteArray is Uint8ClampedList);
   Expect.equals(0, byteArray.length);
 
@@ skipping 260 matching lines @@
     testSetRange();
     testIndexOutOfRange();
     testIndexOf();
     testSubArray();
   }
   testByteArrayRange(true);
   testUnsignedByteArrayRange(true);
   testExternalClampedUnsignedByteArrayRange(true);
 }