Revert "Remove Expect from core library."

tests/compiler/dart2js_extra/operator_test.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.
 
-import "package:expect/expect.dart";
-
 int zero() { return 0; }
 int one() { return 1; }
 int minus1() { return 0 - 1; }
 int two() { return 2; }
 int three() { return 3; }
 int five() { return 5; }
 int minus5() { return 0 - 5; }
 int ninetyNine() { return 99; }
 int four99() { return 499; }
 int four99times99() { return 499 * 99; }
@@ skipping 297 matching lines @@
   orTest();
   xorTest();
   notTest();
   negateTest();
   equalsTest();
   lessTest();
   lessEqualTest();
   greaterTest();
   greaterEqualTest();
 }