Implementation of async-await transformation on js ast.

tests/compiler/dart2js/analyze_helper.dart

 // Copyright (c) 2013, 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 analyze_helper;
 
 import 'dart:async';
 import 'dart:io';
 import 'package:compiler/compiler.dart' as api;
 import 'package:compiler/src/apiimpl.dart';
@@ skipping 136 matching lines @@
 ===
 
 
 """);
 
   var libraryRoot = currentDirectory.resolve('sdk/');
   var packageRoot =
       currentDirectory.resolveUri(new Uri.file('${Platform.packageRoot}/'));
   var provider = new CompilerSourceFileProvider();
   var handler = new CollectingDiagnosticHandler(whiteList, provider);
-  var options = <String>['--analyze-only', '--categories=Client,Server'];
+  var options = <String>['--analyze-only', '--categories=Client,Server',
+    '--show-package-warnings'];
   if (analyzeAll) options.add('--analyze-all');
   var compiler = new Compiler(
       provider.readStringFromUri,
       null,
       handler.diagnosticHandler,
       libraryRoot, packageRoot,
       options,
       {});
   String MESSAGE = """
 
@@ skipping 17 matching lines @@
       exit(1);
     }
   }
   if (analyzeAll) {
     compiler.librariesToAnalyzeWhenRun = uriList;
     return compiler.run(null).then(onCompletion);
   } else {
     return compiler.run(uriList.single).then(onCompletion);
   }
 }