Make autorun notifications work

The code that checks for various conditions is confusing and
undercommented. It appears one of the recent refactorings
inadvertedly inverted the sense of the 'hidden mountpoint'
check, and caused autorun to not work for anything that does
not have a 'native root' - which is pretty much all volumes
implemented by gvfs.

https://bugzilla.gnome.org/show_bug.cgi?id=703418

js/ui/components/autorunManager.js

@@ -31,7 +31,7 @@ function shouldAutorunMount(mount, forTransient) {
     if (!volume || (!volume.allowAutorun && forTransient))
         return false;
 
-    if (!root.is_native() || isMountRootHidden(root))
+    if (root.is_native() && isMountRootHidden(root))
         return false;
 
     return true;