Align semantics of getDefaultConstructor()

pkg/compiler/lib/src/serialization/modelz.dart

 // Copyright (c) 2015, 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.
 
 /// Implementation of the element model used for deserialiation.
 ///
 /// These classes are created by [ElementDeserializer] triggered by the
 /// [Deserializer].
 
 library dart2js.serialization.modelz;
@@ skipping 817 matching lines @@
 
   @override
   bool get hasLocalScopeMembers => _unsupported('hasLocalScopeMembers');
 
   @override
   bool get isEnumClass => false;
 
   @override
   ConstructorElement lookupDefaultConstructor() {
     ConstructorElement constructor = lookupConstructor("");
-    if (constructor != null && constructor.parameters.isEmpty) {
+    if (constructor != null &&
+        constructor.functionSignature.requiredParameterCount == 0) {
       return constructor;
     }
     return null;
   }
 
   @override
   ClassElement get superclass => supertype != null ? supertype.element : null;
 
   @override
   void ensureResolved(Resolution resolution) {
@@ skipping 1406 matching lines @@
   }
 
   @override
   ElementKind get kind => ElementKind.PREFIX;
 
   @override
   Element lookupLocalMember(String memberName) {
     return _unsupported('lookupLocalMember');
   }
 }