Handle use of constant constructors with default values.

tests/compiler/dart2js/serialization/helper.dart

 // Copyright (c) 2016, 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 dart2js.serialization_helper;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/compiler.dart';
 
 import '../memory_compiler.dart';
 import 'test_data.dart';
 
+const String DEFAULT_DATA_FILE_NAME = 'out.data';
+
 class Arguments {
   final String filename;
   final int start;
   final int end;
   final bool loadSerializedData;
   final bool saveSerializedData;
   final String serializedDataFileName;
   final bool verbose;
 
   const Arguments({
     this.filename,
     this.start,
     this.end,
     this.loadSerializedData: false,
     this.saveSerializedData: false,
-    this.serializedDataFileName: 'out.data',
+    this.serializedDataFileName: DEFAULT_DATA_FILE_NAME,
     this.verbose: false});
 
   factory Arguments.from(List<String> arguments) {
     String filename;
     int start;
     int end;
     for (String arg in arguments) {
       if (!arg.startsWith('-')) {
-        int index = int.parse(arg);
+        int index = int.parse(arg, onError: (_) => null);
         if (index == null) {
           filename = arg;
         } else if (start == null) {
           start = index;
         } else {
           end = index;
         }
       }
     }
     bool verbose = arguments.contains('-v');
     bool loadSerializedData = arguments.contains('-l');
     bool saveSerializedData = arguments.contains('-s');
+    if (arguments.contains('--auto')) {
+      File file = new File(DEFAULT_DATA_FILE_NAME);
+      if (file.existsSync()) {
+        loadSerializedData = true;
+      } else {
+        saveSerializedData = true;
+      }
+    }
     return new Arguments(
         filename: filename,
         start: start,
         end: end,
         verbose: verbose,
         loadSerializedData: loadSerializedData,
         saveSerializedData: saveSerializedData);
   }
 
   Future forEachTest(List<Test> tests, Future f(int index, Test test)) async {
@@ skipping 30 matching lines @@
         sink, compiler.libraryLoader.libraries);
     serializedData = sink.text;
     if (arguments.saveSerializedData) {
       File file = new File(arguments.serializedDataFileName);
       print('Saving data to $file');
       file.writeAsStringSync(serializedData);
     }
   }
   return serializedData;
 }