Extend HttpBody handler to support 'multipart/form-data'.

sdk/lib/io/http_multipart_form_data_impl.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 dart.io;
 
 
 class _HttpMultipartFormData extends Stream implements HttpMultipartFormData {
   final ContentType contentType;
   final HeaderValue contentDisposition;
   final HeaderValue contentTransferEncoding;
 
   final MimeMultipart _mimeMultipart;
 
   bool _isText = false;
 
   Stream _stream;
 
   _HttpMultipartFormData(ContentType this.contentType,
                          HeaderValue this.contentDisposition,
                          HeaderValue this.contentTransferEncoding,
                          MimeMultipart this._mimeMultipart) {
     _stream = _mimeMultipart;
     if (contentTransferEncoding != null) {
       // TODO(ajohnsen): Support BASE64, etc.
       throw new HttpException("Unsupported contentTransferEncoding: "
                               "${contentTransferEncoding.value}");
     }
 
-    if (contentType == null || contentType.primaryType == 'text') {
+    if (contentType == null ||
+        contentType.primaryType == 'text' ||
+        contentType.mimeType == 'application/json') {
       _isText = true;
       StringBuffer buffer = new StringBuffer();
       Encoding encoding;
       if (contentType != null) {
         encoding = Encoding.fromName(contentType.charset);
       }
       if (encoding == null) encoding = Encoding.ISO_8859_1;
       _stream = _stream
           .transform(new StringDecoder(encoding))
           .expand((data) {
@@ skipping 50 matching lines @@
                           onDone: onDone,
                           onError: onError,
                           cancelOnError: cancelOnError);
   }
 
   String value(String name) {
     return _mimeMultipart.headers[name];
   }
 }