Handle static fields in js_model/model_test

tests/compiler/dart2js/js_model/model_test.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.
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/kernel/kernel_backend_strategy.dart';
 import 'package:compiler/src/js_model/js_strategy.dart';
 import 'package:expect/expect.dart';
 import '../kernel/compiler_helper.dart';
 import '../serialization/helper.dart';
 
 const Map<String, String> SOURCE = const <String, String>{
   'main.dart': r'''
 foo({named}) => 1;
 bar(a) => !a;
 class Class {
   var field;
+  static var staticField;
 
   Class();
   Class.named(this.field);
 
   method() {}
 }
  
 class SubClass extends Class {
   method() {
     super.method();
   }  
 }
 
 main() {
   foo();
   bar(true);
   [];
   {};
   new Object();
   new Class.named('');
   new SubClass().method();
+  Class.staticField;
+  var x = null;
+  var y1 = x == null;
+  var y2 = null == x;
+  var z1 = x?.toString();
+  var z2 = x ?? y1;
+  var z3 = x ??= y2;
+  return x;
 }
 '''
 };
 
 main(List<String> args) {
   useJsStrategyForTesting = true;
   asyncTest(() async {
     await mainInternal(args);
   });
 }
@@ skipping 14 matching lines @@
   enableDebugMode();
 
   Compiler compiler1 = await compileWithDill(entryPoint, memorySourceFiles, [
     Flags.disableInlining,
     Flags.disableTypeInference
   ], beforeRun: (Compiler compiler) {
     compiler.backendStrategy = new JsBackendStrategy(compiler);
   }, printSteps: true);
   Expect.isFalse(compiler1.compilationFailed);
 }