Start refactoring of the HTTP header handling

runtime/bin/http_parser.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.
 
 // Global constants.
 class _Const {
   // Bytes for "HTTP".
   static final HTTP = const [72, 84, 84, 80];
   // Bytes for "HTTP/1.".
   static final HTTP1DOT = const [72, 84, 84, 80, 47, 49, 46];
@@ skipping 14 matching lines @@
                                              32, 9, 13, 10];
 }
 
 
 // Frequently used character codes.
 class _CharCode {
   static final int HT = 9;
   static final int LF = 10;
   static final int CR = 13;
   static final int SP = 32;
+  static final int COMMA = 44;
   static final int SLASH = 47;
   static final int ZERO = 48;
   static final int ONE = 49;
   static final int COLON = 58;
   static final int SEMI_COLON = 59;
 }
 
 
 // States of the HTTP parser state machine.
 class _State {
@@ skipping 648 matching lines @@
   Function dataEnd;
   Function error;
 }
 
 
 class HttpParserException implements Exception {
   const HttpParserException([String this.message = ""]);
   String toString() => "HttpParserException: $message";
   final String message;
 }