Share a body across all versions of a message.

lib/src/response.dart

Index: lib/src/response.dart
diff --git a/lib/src/response.dart b/lib/src/response.dart
index 55863cba73979dc80c2a8b6aaf984cc3ff764e31..79f8994e444a89ba9f08e5cca26be17328027791 100644
--- a/lib/src/response.dart
+++ b/lib/src/response.dart
@@ -238,7 +238,7 @@ class Response extends Message {
     headers = updateMap(this.headers, headers);
     context = updateMap(this.context, context);
 
-    if (body == null) body = this.read();
+    if (body == null) body = getBody(this);
 
     return new Response(this.statusCode, body: body, headers: headers,
         context: context);