pkg/shelf: spelling fixes

lib/src/message.dart

 // Copyright (c) 2014, 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.
 
 library shelf.message;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:http_parser/http_parser.dart';
@@ skipping 71 matching lines @@
   ///
   /// If [headers] doesn't have a Content-Type header, this will be `null`.
   String get mimeType {
     var contentType = _contentType;
     if (contentType == null) return null;
     return contentType.mimeType;
   }
 
   /// The encoding of the message body.
   ///
-  /// This is parsed from the "charset" paramater of the Content-Type header in
+  /// This is parsed from the "charset" parameter of the Content-Type header in
   /// [headers].
   ///
   /// If [headers] doesn't have a Content-Type header or it specifies an
   /// encoding that [dart:convert] doesn't support, this will be `null`.
   Encoding get encoding {
     var contentType = _contentType;
     if (contentType == null) return null;
     if (!contentType.parameters.containsKey('charset')) return null;
     return Encoding.getByName(contentType.parameters['charset']);
   }
@@ skipping 62 matching lines @@
   if (encoding == null) return headers;
   if (headers['content-type'] == null) {
     return addHeader(headers, 'content-type',
         'application/octet-stream; charset=${encoding.name}');
   }
 
   var contentType = new MediaType.parse(headers['content-type']).change(
       parameters: {'charset': encoding.name});
   return addHeader(headers, 'content-type', contentType.toString());
 }