Fix build break, test forgot to instantiate new constructor

tests/language/src/ConstructorNamedArgumentsTest.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.
 // Dart test program for default constructors.
 
 String message;
 
 foo() {
   message += 'foo';
   return 1;
 }
 
 bar() {
   message += 'bar';
   return 2;
 }
 
 class X {
   var i;
   var j;
   X([a = 'defa', b = 'defb']) : this.i = a, this.j = b;
   X.foo() : this(b: 1, a: 2);
   X.bar() : this(
                      1,  /// 01: runtime error
                      a: 2);
-  X.foobar() : this(1
-                     , a: 2 /// 02: runtime error
-                    );
   X.baz() : this(a: 1, b: 2);
   X.qux() : this(1, 2);
   X.hest() : this();
   X.fisk() : this(b: bar(), a: foo());
   X.naebdyr() : this(a: foo(), b: bar());
 }
 
 test(x, a, b) {
   Expect.equals(x.i, a);
   Expect.equals(x.j, b);
 }
 
 main() {
   test(new X.foo(), 2, 1);
   test(new X.bar(), 2, 'defb');
   test(new X.baz(), 1, 2);
   test(new X.qux(), 1, 2);
   test(new X.hest(), 'defa', 'defb');
 
   message = '';
   new X.fisk();
   Expect.equals('barfoo', message);
 
   message = '';
   new X.naebdyr();
   Expect.equals('foobar', message);
 }