Clear cache for entities referencing a file

Using file entity and media modules I have a link in the body of a node to /file/609. This is automatically rewritten to point to the direct file URL, I assume by the media filter. After replacing the file (via /file/609/edit) the links in the nodes are now stale until a cache flush. Specifically it seems cache_entity_node needs to be cleared for any nodes referencing this file.

The attached patch searches the file_usage table and clears relevant caches after updating a file. Perhaps this would be better suited to the File Entity or Media module, feel free to move it to another queue.