Update charted to 0.4.8 and roll

packages/source_maps/test/vlq_test.dart

 // Copyright (c) 2013, 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 test.vlq_test;
 
 import 'dart:math';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:source_maps/src/vlq.dart';
 
 main() {
   test('encode and decode - simple values', () {
     expect(encodeVlq(1).join(''), 'C');
     expect(encodeVlq(2).join(''), 'E');
     expect(encodeVlq(3).join(''), 'G');
     expect(encodeVlq(100).join(''), 'oG');
     expect(decodeVlq('C'.split('').iterator), 1);
     expect(decodeVlq('E'.split('').iterator), 2);
@@ skipping 23 matching lines @@
     expect(() => encodeVlq(min_int - 1), throws);
     expect(() => encodeVlq(min_int - 2), throws);
 
 
     // if we allowed more than 32 bits, these would be the expected encodings
     // for the large numbers above.
     expect(() => decodeVlq('ggggggE'.split('').iterator), throws);
     expect(() => decodeVlq('igggggE'.split('').iterator), throws);
     expect(() => decodeVlq('jgggggE'.split('').iterator), throws);
     expect(() => decodeVlq('lgggggE'.split('').iterator), throws);
-  });
+  },
+      // This test uses integers so large they overflow in JS.
+      testOn: "dart-vm");
 }
 
 _checkEncodeDecode(int value) {
   var encoded = encodeVlq(value);
   expect(decodeVlq(encoded.iterator), value);
   expect(decodeVlq(encoded.join('').split('').iterator), value);
 }