Add data-URI support class to dart:core (next to Uri).

tests/corelib/uri_ipv4_test.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.
-
-import 'package:expect/expect.dart';
-
-void testParseIPv4Address() {
-  void pass(String host, List<int> out) {
-    Expect.listEquals(Uri.parseIPv4Address(host), out);
-  }
-  void fail(String host) {
-    Expect.throws(() => Uri.parseIPv4Address(host),
-                  (e) => e is FormatException);
-  }
-
-  pass('127.0.0.1', [127, 0, 0, 1]);
-  pass('128.0.0.1', [128, 0, 0, 1]);
-  pass('255.255.255.255', [255, 255, 255, 255]);
-  pass('0.0.0.0', [0, 0, 0, 0]);
-  fail('127.0.0.-1');
-  fail('255.255.255.256');
-  fail('0.0.0.0.');
-  fail('0.0.0.0.0');
-  fail('a.0.0.0');
-  fail('0.0..0');
-}
-
-void main() {
-  testParseIPv4Address();
-}