Remove _HttpUtils from dart:io.

tests/standalone/io/http_cookie_date_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";
 import "dart:async";
 import "dart:math";
 import "dart:collection";
 
 part "../../../sdk/lib/io/common.dart";
 part "../../../sdk/lib/io/io_sink.dart";
 part "../../../sdk/lib/io/http.dart";
 part "../../../sdk/lib/io/http_impl.dart";
 part "../../../sdk/lib/io/http_parser.dart";
-part "../../../sdk/lib/io/http_utils.dart";
+part "../../../sdk/lib/io/http_date.dart";
 part "../../../sdk/lib/io/socket.dart";
 
 void testParseHttpCookieDate() {
-  Expect.throws(() => _HttpUtils.parseCookieDate(""));
+  Expect.throws(() => HttpDate._parseCookieDate(""));
 
   test(int year,
        int month,
        int day,
        int hours,
        int minutes,
        int seconds,
        String formatted) {
     DateTime date = new DateTime.utc(year, month, day, hours, minutes, seconds, 0);
-    Expect.equals(date, _HttpUtils.parseCookieDate(formatted));
+    Expect.equals(date, HttpDate._parseCookieDate(formatted));
   }
 
   test(2012, DateTime.JUNE, 19, 14, 15, 01, "tue, 19-jun-12 14:15:01 gmt");
   test(2021, DateTime.JUNE, 09, 10, 18, 14, "Wed, 09-Jun-2021 10:18:14 GMT");
   test(2021, DateTime.JANUARY, 13, 22, 23, 01, "Wed, 13-Jan-2021 22:23:01 GMT");
   test(2013, DateTime.JANUARY, 15, 21, 47, 38, "Tue, 15-Jan-2013 21:47:38 GMT");
   test(1970, DateTime.JANUARY, 01, 00, 00, 01, "Thu, 01-Jan-1970 00:00:01 GMT");
 }
 
 void main() {
   testParseHttpCookieDate();
 }