Views caching doesn't work properly

The XML backend doesn't support views results caching. Even if you enable typical views cache method based on time, cache instance is never created and request for external source (xml file) are execute for every views show.

What is suprise, output cache works fine.

The problem is that the class views_xml_backend_plugin_query_xml() doesn't implement method get_cache_info(). Implementation from it's parent class - views_plugin_query - return FALSE, so CID (cache identifier for single view) never is created.

I'm preparing patch solves this problem. I will put it here.