Remove dart2js_foreign.

dart/tests/compiler/dart2js_foreign/native_window2_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";
-import 'native_metadata.dart';
-
-abstract class Window {
-  final int document;
-}
-
-// Defining this global object makes Frog eager on optimizing
-// call sites where the receiver is typed 'Window'.
-@Native("@*DOMWindow")
-class _DOMWindowJs implements Window  {
-  final int document;
-}
-
-class Win implements Window {
-}
-
-main() {
-  // By not typing the variable, Frog does not try to optimize calls
-  // on it.
-  var win = new Win();
-  Expect.throws(() => win.document,
-                (e) => e is NoSuchMethodError);
-}