Avoid unneeded toLowerCase and add fast version of _isTokenChar, in HTTP parser.

sdk/lib/io/http_impl.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;
 
 const int _HEADERS_BUFFER_SIZE = 8 * 1024;
 
 class _HttpIncoming extends Stream<List<int>> {
   final int _transferLength;
@@ skipping 706 matching lines @@
   List<Cookie> _cookies;
   _HttpRequest _httpRequest;
   Duration _deadline;
   Timer _deadlineTimer;
 
   _HttpResponse(Uri uri,
                 String protocolVersion,
                 _HttpOutgoing outgoing,
                 String serverHeader)
       : super(uri, protocolVersion, outgoing) {
-    if (serverHeader != null) headers.set('Server', serverHeader);
+    if (serverHeader != null) headers._add('server', serverHeader);
   }
 
   List<Cookie> get cookies {
     if (_cookies == null) _cookies = new List<Cookie>();
     return _cookies;
   }
 
   int get statusCode => _statusCode;
   void set statusCode(int statusCode) {
     if (_headersWritten) throw new StateError("Header already sent");
     _statusCode = statusCode;
   }
 
   String get reasonPhrase => _findReasonPhrase(statusCode);
   void set reasonPhrase(String reasonPhrase) {
     if (_headersWritten) throw new StateError("Header already sent");
     _reasonPhrase = reasonPhrase;
   }
 
   Future redirect(Uri location, {int status: HttpStatus.MOVED_TEMPORARILY}) {
     if (_headersWritten) throw new StateError("Header already sent");
     statusCode = status;
-    headers.set("Location", location.toString());
+    headers.set("location", location.toString());
     return close();
   }
 
   Future<Socket> detachSocket() {
     if (_headersWritten) throw new StateError("Headers already sent");
     deadline = null;  // Be sure to stop any deadline.
     var future = _httpRequest._httpConnection.detachSocket();
     _writeHeaders(drainRequest: false).then((_) => close());
     // Close connection so the socket is 'free'.
     close();
@@ skipping 535 matching lines @@
     var outgoing = new _HttpOutgoing(_socket);
     // Create new request object, wrapping the outgoing connection.
     var request = new _HttpClientRequest(outgoing,
                                          uri,
                                          method,
                                          proxy,
                                          _httpClient,
                                          this);
     request.headers.host = uri.host;
     request.headers.port = port;
-    request.headers.set(HttpHeaders.ACCEPT_ENCODING, "gzip");
+    request.headers._add(HttpHeaders.ACCEPT_ENCODING, "gzip");
     if (_httpClient.userAgent != null) {
-      request.headers.set('User-Agent', _httpClient.userAgent);
+      request.headers._add('user-agent', _httpClient.userAgent);
     }
     if (proxy.isAuthenticated) {
       // If the proxy configuration contains user information use that
       // for proxy basic authorization.
       String auth = _CryptoUtils.bytesToBase64(
           UTF8.encode("${proxy.username}:${proxy.password}"));
       request.headers.set(HttpHeaders.PROXY_AUTHORIZATION, "Basic $auth");
     } else if (!proxy.isDirect && _httpClient._proxyCredentials.length > 0) {
       proxyCreds = _httpClient._findProxyCredentials(proxy);
       if (proxyCreds != null) {
@@ skipping 1235 matching lines @@
 
 String _getHttpVersion() {
   var version = Platform.version;
   // Only include major and minor version numbers.
   int index = version.indexOf('.', version.indexOf('.') + 1);
   version = version.substring(0, index);
   return 'Dart/$version (dart:io)';
 }