Fix HttpBodyHandler to handle missing mimeType.

tests/standalone/io/http_body_test.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.
 
 import 'dart:io';
 import 'dart:utf';
 
 import 'package:expect/expect.dart';
 
 void testHttpClientResponseBody() {
@@ skipping 80 matching lines @@
             dynamic expectedBody,
             String type,
             [bool shouldFail = false]) {
     HttpServer.bind().then((server) {
       server.transform(new HttpBodyHandler())
           .listen((body) {
             if (shouldFail) Expect.fail("Error expected");
             Expect.equals(type, body.type);
             switch (type) {
               case "text":
+                Expect.equals(body.mimeType, "text/plain");
                 Expect.equals(expectedBody, body.body);
                 break;
 
               case "json":
+                Expect.equals(body.mimeType, "application/json");
                 Expect.mapEquals(expectedBody, body.body);
                 break;
 
+              case "binary":
+                Expect.equals(body.mimeType, null);
+                Expect.listEquals(expectedBody, body.body);
+                break;
+
               default:
                 Expect.fail("bad body type");
             }
             body.response.close();
           }, onError: (error) {
             if (!shouldFail) Expect.fail("Error unexpected");
           });
 
       var client = new HttpClient();
       client.post("127.0.0.1", server.port, "/")
           .then((request) {
-            request.headers.contentType =
-                new ContentType.fromString(mimeType);
+            if (mimeType != null) {
+              request.headers.contentType =
+                  new ContentType.fromString(mimeType);
+            }
             request.add(content);
             return request.close();
           })
           .then((response) {
             if (shouldFail) {
               Expect.equals(HttpStatus.BAD_REQUEST, response.statusCode);
             }
             response.fold(null, (x, y) {});
             client.close();
             server.close();
@@ skipping 14 matching lines @@
 
   test("application/json",
        '{"val": 5}'.codeUnits,
        { "val" : 5 },
        "json");
   test("application/json",
        '{ bad json }'.codeUnits,
        null,
        "json",
        true);
+
+  test(null, "body".codeUnits, "body".codeUnits, "binary");
 }
 
 
 void main() {
   testHttpClientResponseBody();
   testHttpServerRequestBody();
 }