Add most equivalence tests to js_model/model_test

pkg/compiler/lib/src/kernel/kelements.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.
 
 /// Entity model for elements derived from Kernel IR.
 
 import '../elements/entities.dart';
 import '../elements/names.dart';
 import '../elements/types.dart';
 import 'elements.dart';
@@ skipping 210 matching lines @@
   KField(int memberIndex, KLibrary library, KClass enclosingClass, Name name,
       {bool isStatic, this.isAssignable, this.isConst})
       : super(memberIndex, library, enclosingClass, name, isStatic: isStatic);
 
   @override
   bool get isField => true;
 
   String get _kind => 'field';
 }
 
-class KTypeVariable implements TypeVariableEntity {
+class KTypeVariable implements TypeVariableEntity, IndexedTypeVariable {
   final Entity typeDeclaration;
   final String name;
   final int index;
 
   KTypeVariable(this.typeDeclaration, this.name, this.index);
 
   String toString() =>
       '${kElementPrefix}type_variable(${typeDeclaration.name}.$name)';
 }
 
 class KLocalFunction implements Local {
   final String name;
   final MemberEntity memberContext;
   final Entity executableContext;
   final FunctionType functionType;
 
   KLocalFunction(
       this.name, this.memberContext, this.executableContext, this.functionType);
 
   String toString() =>
       '${kElementPrefix}local_function(${memberContext.name}.${name ?? '<anonymous>'})';
 }