Properly retrieve and expose HttpServletResponse for async requests

Issue: SPR-15867

spring-webmvc/src/main/java/org/springframework/web/servlet/FrameworkServlet.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -1133,8 +1133,9 @@ public abstract class FrameworkServlet extends HttpServletBean implements Applic
 		public <T> void preProcess(NativeWebRequest webRequest, Callable<T> task) {
 			HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
 			if (request != null) {
-				HttpServletResponse response = webRequest.getNativeRequest(HttpServletResponse.class);
+				HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
-				initContextHolders(request, buildLocaleContext(request), buildRequestAttributes(request, response, null));
+				initContextHolders(request, buildLocaleContext(request),
+						buildRequestAttributes(request, response, null));
 			}
 		}
 		@Override