Latent bug revealed by 614ea7e6;
Now that cross-context calls go through disp_call* instead of
jsdisp_call*, and thus through InvokeEx, the `this` pointer is
lost when calling methods inherited from a prototype.
Signed-off-by: Kevin Puetz <PuetzKevinA@JohnDeere.com>
Signed-off-by: Jacek Caban <jacek@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>