Finish strong mode cleaning of dart2js.

pkg/compiler/lib/src/serialization/constant_serialization.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.
 
 library dart2js.serialization.constants;
 
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../elements/elements.dart'
     show ConstructorElement, FieldElement, LocalVariableElement, MethodElement;
+import '../elements/entities.dart' show FieldEntity;
 import '../elements/operators.dart';
 import '../elements/resolution_types.dart';
 import '../universe/call_structure.dart' show CallStructure;
 import 'keys.dart';
 import 'serialization.dart';
 
 /// Visitor that serializes a [ConstantExpression] by encoding it into an
 /// [ObjectEncoder].
 ///
 /// This class is called from the [Serializer] when a [ConstantExpression] needs
@@ skipping 297 matching lines @@
   @override
   void visitGenerative(
       GenerativeConstantConstructor constructor, ObjectEncoder encoder) {
     ResolutionInterfaceType type = constructor.type;
     encoder.setType(Key.TYPE, type);
     MapEncoder defaults = encoder.createMap(Key.DEFAULTS);
     constructor.defaultValues.forEach((key, e) {
       defaults.setConstant('$key', e);
     });
     ListEncoder fields = encoder.createList(Key.FIELDS);
-    constructor.fieldMap.forEach((FieldElement f, ConstantExpression e) {
+    constructor.fieldMap.forEach((FieldEntity _f, ConstantExpression e) {
+      FieldElement f = _f;
       ObjectEncoder fieldSerializer = fields.createObject();
       fieldSerializer.setElement(Key.FIELD, f);
       fieldSerializer.setConstant(Key.CONSTANT, e);
     });
     if (constructor.superConstructorInvocation != null) {
       encoder.setConstant(
           Key.CONSTRUCTOR, constructor.superConstructorInvocation);
     }
   }
 
@@ skipping 79 matching lines @@
             type, readDefaults(), readFields(), readConstructorInvocation());
       case ConstantConstructorKind.REDIRECTING_GENERATIVE:
         return new RedirectingGenerativeConstantConstructor(
             readDefaults(), readConstructorInvocation());
       case ConstantConstructorKind.REDIRECTING_FACTORY:
         return new RedirectingFactoryConstantConstructor(
             readConstructorInvocation());
     }
   }
 }