Revert "Remove Expect from core library."

tests/language/parameter_initializer2_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";
-
 // Test Parameter Intializer.
 
 
 class ParameterInitializer2Test {
   static testMain() {
     var a = new A(123);
     Expect.equals(123, a.x);
 
     var b = new B(123);
     Expect.equals(123, b.x);
@@ skipping 58 matching lines @@
   int y_;
   int w_;
   int z;
   int az_;
 }
 
 
 main() {
   ParameterInitializer2Test.testMain();
 }