Fix tests for VM in checked mode.

runtime/lib/integers_patch.dart

 // Copyright (c) 2012, 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.
 // Dart core library.
 
 // VM implementation of int.
 
 patch class int {
   static int _parse(String str) native "Integer_parse";
 
-  static void _throwFormatException(String source) {
+  static int _throwFormatException(String source) {
     throw new FormatException(source);
   }
 
   /* patch */ static int parse(String source,
                                { int radix,
                                  int onError(String str) }) {
     if (source is! String) throw new ArgumentError(source);
     if (radix == null) {
       if (onError == null) return _parse(source);
       try {
@@ skipping 40 matching lines @@
       int digit = digits[code - 0x30];
       if (digit >= radix) return onError(source);
       result = result * radix + digit;
       i++;
       if (i == source.length) break;
       code = source.charCodeAt(i);
     } while (true);
     return negative ? -result : result;
   }
 }