Remove dart2js_foreign.

dart/tests/compiler/dart2js_foreign/native_null_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.
-
-// Test that parameters in native methods are not mangled. This test is needed
-// until we change all libraries to using the JS foreign element.
-
-import "package:expect/expect.dart";
-import 'native_metadata.dart';
-
-@Native("*A")
-class A {
-  @Native("return null;")
-  returnNull();
-  @Native("return undefined;")
-  returnUndefined();
-  @Native("return '';")
-  returnEmptyString();
-  @Native("return 0;")
-  returnZero();
-}
-
-@native A makeA();
-
-@Native("""
-function A() {}
-makeA = function(){return new A;};
-""")
-void setup();
-
-
-main() {
-  setup();
-  A a = makeA();
-  Expect.equals(null, a.returnNull());
-  Expect.equals(null, a.returnUndefined());
-
-  Expect.equals('', a.returnEmptyString());
-  Expect.isTrue(a.returnEmptyString().isEmpty);
-  Expect.isTrue(a.returnEmptyString() is String);
-
-  Expect.isTrue(a.returnZero() is int);
-  Expect.equals(0, a.returnZero());
-}