Expand usage of defaultEncoding in HttpBody in the http_server package.

pkg/http_server/lib/src/http_multipart_form_data.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.
 
 part of http_server;
 
 
 /**
  * [:HttpMultipartFormData:] class used for 'upgrading' a [MimeMultipart] by
  * parsing it as a 'multipart/form-data' part. The following code shows how
@@ skipping 49 matching lines @@
    *
    * Use this method to index other headers available in the original
    * [MimeMultipart].
    */
   String value(String name);
 
   /**
    * Parse a [MimeMultipart] and return a [HttpMultipartFormData]. If the
    * [:Content-Disposition:] header is missing or invalid, a [HttpException] is
    * thrown.
+   *
+   * If the [MimeMultipart] is identified as text, and the [:Content-Type:]
+   * header is missing, the data is decoded using [defaultEncoding]. See more
+   * information in the
+   * [HTML5 spec](http://dev.w3.org/html5/spec-preview/
+   * constraints.html#multipart-form-data).
    */
-  static HttpMultipartFormData parse(MimeMultipart multipart)
-      => _HttpMultipartFormData.parse(multipart);
+  static HttpMultipartFormData parse(MimeMultipart multipart,
+                                     {Encoding defaultEncoding: UTF8})
+      => _HttpMultipartFormData.parse(multipart, defaultEncoding);
 }