Remove _HttpUtils from dart:io.

sdk/lib/io/http_headers.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.
 
 part of dart.io;
 
 class _HttpHeaders implements HttpHeaders {
   _HttpHeaders(String this.protocolVersion)
       : _headers = new Map<String, List<String>>();
 
@@ skipping 698 matching lines @@
       }
 
       while (!done()) {
         String name = parseAttributeName();
         String value = "";
         if (!done() && s[index] == "=") {
           index++;  // Skip the = character.
           value = parseAttributeValue();
         }
         if (name == "expires") {
-          expires = _HttpUtils.parseCookieDate(value);
+          expires = HttpDate._parseCookieDate(value);
         } else if (name == "max-age") {
           maxAge = int.parse(value);
         } else if (name == "domain") {
           domain = value;
         } else if (name == "path") {
           path = value;
         } else if (name == "httponly") {
           httpOnly = true;
         } else if (name == "secure") {
           secure = true;
@@ skipping 41 matching lines @@
 
   String name;
   String value;
   DateTime expires;
   int maxAge;
   String domain;
   String path;
   bool httpOnly = false;
   bool secure = false;
 }