Add J-elements

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/js_model/js_strategy.dart';
@@ skipping 26 matching lines @@
     memorySourceFiles = SOURCE;
   }
 
   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);
 }