Tests for `void`.

pkg/compiler/lib/src/js_backend/backend_helpers.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.js_backend.helpers;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers, Uris;
 import '../compiler.dart' show Compiler;
 import '../core_types.dart' show CommonElements, ElementEnvironment;
@@ skipping 147 matching lines @@
       _jsStringClass ??= _findInterceptorsClass('JSString');
 
   ClassEntity _jsArrayClass;
   ClassEntity get jsArrayClass =>
       _jsArrayClass ??= _findInterceptorsClass('JSArray');
 
   ClassEntity _jsNumberClass;
   ClassEntity get jsNumberClass =>
       _jsNumberClass ??= _findInterceptorsClass('JSNumber');
 
+  ClassEntity _voidClass;
+  ClassEntity get voidClass =>
+      _voidClass ??= _findHelperClass("Void");
+
   ClassEntity _jsIntClass;
   ClassEntity get jsIntClass => _jsIntClass ??= _findInterceptorsClass('JSInt');
 
   ClassEntity _jsDoubleClass;
   ClassEntity get jsDoubleClass =>
       _jsDoubleClass ??= _findInterceptorsClass('JSDouble');
 
   ClassEntity _jsNullClass;
   ClassEntity get jsNullClass =>
       _jsNullClass ??= _findInterceptorsClass('JSNull');
@@ skipping 596 matching lines @@
   ClassEntity get annotationReturnsClass => _findHelperClass('Returns');
 
   ClassEntity get annotationJSNameClass => _findHelperClass('JSName');
 
   FunctionEntity get toStringForNativeObject =>
       _findHelperFunction('toStringForNativeObject');
 
   FunctionEntity get hashCodeForNativeObject =>
       _findHelperFunction('hashCodeForNativeObject');
 }