Add ElementKind for factory constructors.

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 33 matching lines @@
 /// Compute a [Link] from an [Iterable].
 Link toLink(Iterable iterable) {
   LinkBuilder builder = new LinkBuilder();
   for (var element in iterable) {
     builder.addLast(element);
   }
   return builder.toLink();
 }
 
 abstract class ElementZ extends Element with ElementCommon {
-  @override
-  bool get isFactoryConstructor => false;
-
   String toString() {
     if (enclosingElement == null || isTopLevel) return 'Z$kind($name)';
     return 'Z$kind(${enclosingElement.name}#$name)';
   }
 
   _unsupported(text) => throw new UnsupportedError('${this}.$text');
 
   @override
   AnalyzableElement get analyzableElement {
     Element element = this;
@@ skipping 932 matching lines @@
   @override
   ElementKind get kind => ElementKind.GENERATIVE_CONSTRUCTOR;
 }
 
 class FactoryConstructorElementZ extends ConstructorElementZ {
 
   FactoryConstructorElementZ(ObjectDecoder decoder)
       : super(decoder);
 
   @override
-  ElementKind get kind => ElementKind.FUNCTION;
-
-  @override
-  bool get isFactoryConstructor => true;
+  ElementKind get kind => ElementKind.FACTORY_CONSTRUCTOR;
 }
 
 abstract class MemberElementMixin
     implements DeserializedElementZ, MemberElement {
 
   @override
   MemberElement get memberContext => this;
 
   @override
   Name get memberName => new Name(name, library);
@@ skipping 549 matching lines @@
   }
 
   @override
   ElementKind get kind => ElementKind.PREFIX;
 
   @override
   Element lookupLocalMember(String memberName) {
     return _unsupported('lookupLocalMember');
   }
 }