Register created closure class with the world.

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

 // Copyright (c) 2017, 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.js_model.elements;
 
 import '../elements/entities.dart';
 import '../elements/names.dart';
 import '../elements/types.dart';
 import '../kernel/elements.dart';
@@ skipping 305 matching lines @@
   JClass(this.library, this.classIndex, this.name, {this.isAbstract});
 
   @override
   bool get isClosure => false;
 
   String toString() => '${jsElementPrefix}class($name)';
 }
 
 abstract class JMember implements MemberEntity, IndexedMember {
   /// Member index used for fast lookup in [JsToFrontendMapImpl].
-  final int memberIndex;
+  int _memberIndex;
   final JLibrary library;
   final JClass enclosingClass;
   final Name _name;
   final bool _isStatic;
 
-  JMember(this.memberIndex, this.library, this.enclosingClass, this._name,
+  JMember(this._memberIndex, this.library, this.enclosingClass, this._name,
       {bool isStatic: false})
       : _isStatic = isStatic;
 
+  int get memberIndex => _memberIndex;
+
+  /// Should only be called by closure methods. All others should set
+  /// memberIndex at initialization time.
+  void set setClosureMemberIndex(int newIndex) {
+    _memberIndex = newIndex;
+  }
+
   String get name => _name.text;
 
   Name get memberName => _name;
 
   @override
   bool get isAssignable => false;
 
   @override
   bool get isConst => false;
 
@@ skipping 199 matching lines @@
   final MemberEntity memberContext;
   final Entity executableContext;
   final FunctionType functionType;
 
   JLocalFunction(
       this.name, this.memberContext, this.executableContext, this.functionType);
 
   String toString() => '${jsElementPrefix}local_function'
       '(${memberContext.name}.${name ?? '<anonymous>'})';
 }