Expose whether a file is public to WB via

 download_url in `addon_view_file()`, which is
 called by `addon_view_or_download_file()`.
 The `is_public` comes from the node to which
 the file belongs.

Author: cslzchen

addons/base/views.py

@@ -732,6 +732,7 @@ def addon_view_file(auth, node, file_node, version):
             'direct': None,
             'mode': 'render',
             'action': 'download',
+            'public_file': node.is_public,
         })
     )