Enable async support

pkg/analyzer/test/options_test.dart

Index: pkg/analyzer/test/options_test.dart
diff --git a/pkg/analyzer/test/options_test.dart b/pkg/analyzer/test/options_test.dart
index 12818c5115bc13cce67abab46911ed9fc0ec1961..5f1bfd6ae51411a97c5939c6fd42337b22c7843e 100644
--- a/pkg/analyzer/test/options_test.dart
+++ b/pkg/analyzer/test/options_test.dart
@@ -18,7 +18,6 @@ main() {
       expect(options.dartSdkPath, isNotNull);
       expect(options.disableHints, isFalse);
       expect(options.displayVersion, isFalse);
-      expect(options.enableAsync, isFalse);
       expect(options.enableEnum, isFalse);
       expect(options.enableTypeChecks, isFalse);
       expect(options.ignoreUnrecognizedFlags, isFalse);
@@ -47,12 +46,6 @@ main() {
       expect(options.definedVariables['bar'], isNull);
     });
 
-    test('enable async', () {
-      CommandLineOptions options =
-          CommandLineOptions.parse(['--dart-sdk', '.', '--enable-async', 'foo.dart']);
-      expect(options.enableAsync, isTrue);
-    });
-
     test('enable enum', () {
       CommandLineOptions options =
           CommandLineOptions.parse(['--dart-sdk', '.', '--enable-enum', 'foo.dart']);