Expand usage of defaultEncoding in HttpBody in the http_server package.

pkg/http_server/lib/src/http_body_impl.dart

Index: pkg/http_server/lib/src/http_body_impl.dart
diff --git a/pkg/http_server/lib/src/http_body_impl.dart b/pkg/http_server/lib/src/http_body_impl.dart
index f3ffa9e7252d7d7a2c1d8c826e5ab7e2cdcb0566..227c60393949fcc0862fa870c91a6f5904d5c009 100644
--- a/pkg/http_server/lib/src/http_body_impl.dart
+++ b/pkg/http_server/lib/src/http_body_impl.dart
@@ -67,7 +67,8 @@ class _HttpBodyHandler {
       return stream
           .transform(new MimeMultipartTransformer(
                 contentType.parameters['boundary']))
-          .map((HttpMultipartFormData.parse))
+          .map((part) => HttpMultipartFormData.parse(
+                part, defaultEncoding: defaultEncoding))
           .map((multipart) {
             var future;
             if (multipart.isText) {
@@ -107,7 +108,7 @@ class _HttpBodyHandler {
 
     switch (contentType.primaryType) {
       case "text":
-        return asText(ASCII);
+        return asText(defaultEncoding);
 
       case "application":
         switch (contentType.subType) {