Fix Class isAssignableFrom checks for Resource conversion

Issue: SPR-16606

spring-web/src/main/java/org/springframework/http/converter/ResourceHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -86,7 +86,7 @@ public class ResourceHttpMessageConverter extends AbstractHttpMessageConverter<R
 				}
 			};
 		}
-		else if (clazz.isAssignableFrom(ByteArrayResource.class)) {
+		else if (Resource.class == clazz || ByteArrayResource.class.isAssignableFrom(clazz)) {
 			byte[] body = StreamUtils.copyToByteArray(inputMessage.getBody());
 			return new ByteArrayResource(body) {
 				@Override