Let parser handle factory modifiers.

pkg/front_end/test/fasta/bootstrap_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' show
     Future;
 
 import 'dart:io' show
     Directory,
     Platform;
 
 import 'dart:isolate' show
     Isolate;
 
 import 'package:async_helper/async_helper.dart' show
     asyncEnd,
     asyncStart;
 
 import 'package:front_end/src/fasta/testing/kernel_chain.dart' show
     computePatchedSdk;
 
 import 'package:testing/testing.dart' show
     StdioProcess;
 
 Future main() async {
   asyncStart();
   Uri sourceCompiler = await Isolate.resolvePackageUri(
       Uri.parse("package:front_end/src/fasta/bin/compile.dart"));
   Uri packages = await Isolate.packageConfig;
+  Directory tmp = await Directory.systemTemp.createTemp("fasta_bootstrap");
+  Uri compiledOnceCompiler = tmp.uri.resolve("fasta1.dill");
+  Uri compiledTwiceCompiler = tmp.uri.resolve("fasta2.dill");
   try {
-    Directory tmp = await Directory.systemTemp.createTemp("fasta_bootstrap");
-    Uri compiledOnceCompiler = tmp.uri.resolve("fasta1.dill");
-    Uri compiledTwiceCompiler = tmp.uri.resolve("fasta2.dill");
-    try {
-      await runCompiler(sourceCompiler, sourceCompiler, compiledOnceCompiler);
-      await runCompiler(
-          compiledOnceCompiler, sourceCompiler, compiledTwiceCompiler);
-    } finally {
-      await tmp.delete(recursive: true);
-    }
+    await runCompiler(sourceCompiler, sourceCompiler, compiledOnceCompiler);
+    await runCompiler(
+        compiledOnceCompiler, sourceCompiler, compiledTwiceCompiler);
   } finally {
-    asyncEnd();
+    await tmp.delete(recursive: true);
   }
+  asyncEnd();
 }
 
 Future runCompiler(Uri compiler, Uri input, Uri output) async {
   Uri patchedSdk = await computePatchedSdk();
   Uri dartVm = Uri.base.resolve(Platform.resolvedExecutable);
   StdioProcess result = await StdioProcess.run(
       dartVm.toFilePath(),
       <String>[
+          "-c",
           compiler.toFilePath(),
           "--compile-sdk=${patchedSdk.toFilePath()}",
           "--output=${output.toFilePath()}",
+          "--verify",
           input.toFilePath(),
         ]);
   print(result.output);
   if (result.exitCode != 0) {
     throw "Compilation failed.";
   }
 }