Revert "Remove Expect from core library."

tests/compiler/dart2js_extra/named_parameter_for_static_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.
 
-import "package:expect/expect.dart";
-
 oneOptionalArgument(a, {b}) {
   Expect.equals(1, a);
   Expect.equals(2, b);
 }
 
 twoOptionalArguments({a, b}) {
   Expect.equals(1, a);
   Expect.equals(2, b);
 }
 
@@ skipping 45 matching lines @@
 class B extends A {
   B.one() : super.twoOptionalArguments(a: 1, b: 2);
   B.two() : super.twoOptionalArguments(b: 2, a: 1);
   B.three() : super.oneOptionalArgument(1, b: 2);
 
   B();
   B_one() { super.twoOptArgs(a: 1, b: 2); }
   B_two() { super.twoOptArgs(b: 2, a: 1); }
   B_three() { super.oneOptArg(1, b: 2); }
 }