Implementation of async-await transformation on js ast.

tests/compiler/dart2js/mock_compiler.dart

 // Copyright (c) 2012, 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 mock_compiler;
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import 'dart:collection';
 
@@ skipping 74 matching lines @@
               enableMinification: enableMinification,
               enableConcreteTypeInference: enableConcreteTypeInference,
               maxConcreteTypeSize: maxConcreteTypeSize,
               disableTypeInferenceFlag: disableTypeInference,
               analyzeAllFlag: analyzeAll,
               analyzeOnly: analyzeOnly,
               emitJavaScript: emitJavaScript,
               preserveComments: preserveComments,
               trustTypeAnnotations: trustTypeAnnotations,
               showPackageWarnings: true,
-              outputProvider: outputProvider,
-              enableAsyncAwait: enableAsyncAwait) {
+              outputProvider: outputProvider) {
     this.disableInlining = disableInlining;
 
     deferredLoadTask = new MockDeferredLoadTask(this);
 
     clearMessages();
 
     registerSource(Compiler.DART_CORE,
                    buildLibrarySource(DEFAULT_CORE_LIBRARY, coreSource));
     registerSource(PATCH_CORE, DEFAULT_PATCH_CORE_SOURCE);
 
@@ skipping 287 matching lines @@
   MockElement(Element enclosingElement)
       : super('', ElementKind.FUNCTION, Modifiers.EMPTY,
               enclosingElement, false);
 
   get node => null;
 
   parseNode(_) => null;
 
   bool get hasNode => false;
 }