Incremental compilation of added instance fields.

dart/pkg/compiler/lib/src/elements/modelx.dart

 // Copyright (c) 2013, 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.
 
 library elements.modelx;
 
 import 'elements.dart';
 import '../constants/expressions.dart';
 import '../helpers/helpers.dart';  // Included for debug helpers.
 import '../tree/tree.dart';
@@ skipping 1243 matching lines @@
             variables, name.token);
 
   accept(ElementVisitor visitor) => visitor.visitFieldElement(this);
 
   MemberElement get memberContext => this;
 
   void reuseElement() {
     super.reuseElement();
     nestedClosures.clear();
   }
+
+  FieldElementX copyWithEnclosing(Element enclosingElement) {
+    return new FieldElementX(
+        new Identifier(token), enclosingElement, variables);
+  }
 }
 
 /// [Element] for a parameter-like element.
 class FormalElementX extends ElementX
     with AstElementMixin
     implements FormalElement {
   final VariableDefinitions definitions;
   final Identifier identifier;
   DartType typeCache;
 
@@ skipping 1545 matching lines @@
   AstElement get definingElement;
 
   bool get hasResolvedAst => definingElement.hasTreeElements;
 
   ResolvedAst get resolvedAst {
     return new ResolvedAst(declaration,
         definingElement.node, definingElement.treeElements);
   }
 
 }