Simplify parsing of 'new' operator.

tests/language/src/Factory4Test.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.
+
+interface Link<T> default LinkFactory {
+  Link.create();
+}
+
+class A<T> { }
+
+class LinkFactory<T> extends A<T> {
+  factory Link.create() {
+    return null;
+  }
+}
+
+main() {
+  var a = new Link<int>.create();
+}