add parser parseAsync flag

pkg/analyzer/test/src/task/dart_test.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 analyzer.test.src.task.dart_test;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/dart/element/element.dart';
@@ skipping 2975 matching lines @@
     expect(outputs[EXPORTED_LIBRARIES], hasLength(0));
     _assertHasCore(outputs[IMPORTED_LIBRARIES], 1);
     expect(outputs[INCLUDED_PARTS], hasLength(0));
     expect(outputs[LIBRARY_SPECIFIC_UNITS], hasLength(1));
     expect(outputs[PARSE_ERRORS], hasLength(0));
     expect(outputs[PARSED_UNIT], isNotNull);
     expect(outputs[SOURCE_KIND], SourceKind.PART);
     expect(outputs[UNITS], hasLength(1));
   }
 
+  test_perform_enableAsync_false() {
+    AnalysisOptionsImpl options = new AnalysisOptionsImpl();
+    options.enableAsync = false;
+    prepareAnalysisContext(options);
+    _performParseTask(r'''
+import 'dart:async';
+class B {void foo() async {}}''');
+    expect(outputs, hasLength(9));
+    expect(outputs[EXPLICITLY_IMPORTED_LIBRARIES], hasLength(1));
+    expect(outputs[EXPORTED_LIBRARIES], hasLength(0));
+    _assertHasCore(outputs[IMPORTED_LIBRARIES], 2);
+    expect(outputs[INCLUDED_PARTS], hasLength(0));
+    expect(outputs[LIBRARY_SPECIFIC_UNITS], hasLength(1));
+    expect(outputs[PARSE_ERRORS], hasLength(1));
+    expect(outputs[PARSED_UNIT], isNotNull);
+    expect(outputs[SOURCE_KIND], SourceKind.LIBRARY);
+    expect(outputs[UNITS], hasLength(1));
+  }
+
+  test_perform_enableAsync_true() {
+    _performParseTask(r'''
+import 'dart:async';
+class B {void foo() async {}}''');
+    expect(outputs, hasLength(9));
+    expect(outputs[EXPLICITLY_IMPORTED_LIBRARIES], hasLength(1));
+    expect(outputs[EXPORTED_LIBRARIES], hasLength(0));
+    _assertHasCore(outputs[IMPORTED_LIBRARIES], 2);
+    expect(outputs[INCLUDED_PARTS], hasLength(0));
+    expect(outputs[LIBRARY_SPECIFIC_UNITS], hasLength(1));
+    expect(outputs[PARSE_ERRORS], hasLength(0));
+    expect(outputs[PARSED_UNIT], isNotNull);
+    expect(outputs[SOURCE_KIND], SourceKind.LIBRARY);
+    expect(outputs[UNITS], hasLength(1));
+  }
+
   test_perform_computeSourceKind_noDirectives_hasContainingLibrary() {
     // Parse "lib.dart" to let the context know that "test.dart" is included.
     computeResult(
         newSource(
             '/lib.dart',
             r'''
 library lib;
 part 'test.dart';
 '''),
         PARSED_UNIT);
@@ skipping 1805 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result];
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }