One more factory -> default pass.

dart/tests/language/src/FactoryImplementationTest.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 A factory B {
+interface A default B {
   A(int x, int y);
 }
 
-interface X factory B {
+interface X default B {
   X(int x, int y);
 }
 
 class XImpl implements X {
   final int x;
   final int y;
   XImpl(this.x, this.y);
 }
 
 // new A invokes B constructor because B implements A.
@@ skipping 13 matching lines @@
   var a = new A(1, 2);
   // Check that constructor B is invoked and not factory A.
   Expect.equals(1, a.x);
   Expect.equals(2, a.y);
 
   var x = new X(11, 22);
   // Check that factory is invoked.
   Expect.equals(110, x.x);
   Expect.equals(220, x.y);
 }