According to the ES6 spec, it should work in generic way for objects exposing
"source" and "flags", but native IE seems to not follow it here and throws.
Signed-off-by: Gabriel Ivăncescu <gabrielopcode@gmail.com>
Signed-off-by: Jacek Caban <jacek@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>