Add the HttpBodyHandler files to the dart:io library

tests/standalone/io/http_body_test.dart

Index: tests/standalone/io/http_body_test.dart
diff --git a/tests/standalone/io/http_body_test.dart b/tests/standalone/io/http_body_test.dart
index ae0d128242965fb8f3ce586a499f35d9b680b3d0..22a22ecff5f1963e40a3cd5dc799c0b47f94d455 100644
--- a/tests/standalone/io/http_body_test.dart
+++ b/tests/standalone/io/http_body_test.dart
@@ -8,7 +8,6 @@ import 'dart:utf';
 import 'package:expect/expect.dart';
 
 void testHttpClientResponseBody() {
-  new HttpBodyHandler();
   void test(String mimeType,
             List<int> content,
             dynamic expectedBody,
@@ -165,7 +164,6 @@ void testHttpServerRequestBody() {
   test(null, "body".codeUnits, "body".codeUnits, "binary");
 }
 
-
 void main() {
   testHttpClientResponseBody();
   testHttpServerRequestBody();