All strong mode cleaning of dart2js.

pkg/compiler/lib/src/js_backend/field_naming_mixin.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.
 
 part of js_backend.namer;
 
 abstract class _MinifiedFieldNamer implements Namer {
   _FieldNamingRegistry get fieldRegistry;
 
   // Returns a minimal name for the field that is globally unique along
@@ skipping 79 matching lines @@
  * This is achieved at construction time via the [_fieldNameCounter] field that
  * counts the number of fields on the path to the root node that have been
  * encountered so far.
  *
  * Obviously, this only works if no fields are added to a parent node after its
  * children have added their first field.
  */
 class _FieldNamingScope {
   final _FieldNamingScope superScope;
   final Entity container;
-  final Map<Element, jsAst.Name> names = new Maplet<Element, jsAst.Name>();
+  final Map<Entity, jsAst.Name> names = new Maplet<Entity, jsAst.Name>();
   final _FieldNamingRegistry registry;
 
   /// Naming counter used for fields of ordinary classes.
   int _fieldNameCounter;
 
   /// The number of fields along the superclass chain that use inheritance
   /// based naming, including the ones allocated for this scope.
   int get inheritanceBasedFieldNameCounter => _fieldNameCounter;
 
   /// The number of locally used fields. Depending on the naming source
@@ skipping 114 matching lines @@
       : super.rootScope(box, registry);
 
   @override
   bool containsField(_) => true;
 
   jsAst.Name operator [](Element field) {
     if (!names.containsKey(field)) add(field);
     return names[field];
   }
 }