Properly resynthesize field formal parameter elements.

pkg/analyzer/lib/src/dart/element/element.dart

 // Copyright (c) 2014, 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 analyzer.src.dart.element.element;
 
 import 'dart:collection';
 import 'dart:math' show min;
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2490 matching lines @@
  * [FieldElement] associated with the parameter.
  */
 class FieldFormalParameterElementImpl extends ParameterElementImpl
     implements FieldFormalParameterElement {
   /**
    * The field associated with this field formal parameter.
    */
   FieldElement field;
 
   /**
+   * Initialize a newly created parameter element to have the given [name] and
+   * [offset].
+   */
+  FieldFormalParameterElementImpl.forNameAndOffset(String name, int nameOffset)
+      : super(name, nameOffset);
+
+  /**
    * Initialize a newly created parameter element to have the given [name].
    */
   FieldFormalParameterElementImpl(Identifier name) : super.forNode(name);
 
   @override
   bool get isInitializingFormal => true;
 
   @override
   accept(ElementVisitor visitor) =>
       visitor.visitFieldFormalParameterElement(this);
@@ skipping 2067 matching lines @@
 
   @override
   void visitElement(Element element) {
     int offset = element.nameOffset;
     if (offset != -1) {
       map[offset] = element;
     }
     super.visitElement(element);
   }
 }