Record default clause for interfaces in parser.

tests/compiler/dart2js/unparser_test.dart

Index: tests/compiler/dart2js/unparser_test.dart
diff --git a/tests/compiler/dart2js/unparser_test.dart b/tests/compiler/dart2js/unparser_test.dart
index 6bdb32dee4e081a2b9e30073adbcbb3c94022008..408d9d241e061a933a071538fae1778aa5ca2cd1 100644
--- a/tests/compiler/dart2js/unparser_test.dart
+++ b/tests/compiler/dart2js/unparser_test.dart
@@ -167,6 +167,11 @@ testFactoryConstructor() {
   // Now more complicated, with normal constructor and factory parameters.
   testDart2Dart('main(){new A.fromFoo(5);}'
       'class A{A(this.f);A.fromFoo(foo):this("f");final String f;}');
+  // Now even more complicated, with interface and default factory.
+  testDart2Dart('main(){new A.fromFoo(5); new I.fromFoo();}'
+      'class IFactory{factory I.fromFoo()=> new A(5);}'
+      'interface I default IFactory{I.fromFoo();}'
+      'class A implements I{A(this.f);A.fromFoo(foo):this("f");final String f;}');
 }
 
 main() {