importer: Use new JS_GetOwnPropertyDescriptor()
importer: Use new JS_GetOwnPropertyDescriptor()

Technically it was incorrect to use JS_GetPropertyDescriptorById() here
although it was unlikely to cause any problems.

https://bugzilla.gnome.org/show_bug.cgi?id=751252

endlessm/gjs,endlessm/gjs,endlessm/gjs,endlessm/gjs,endlessm/gjs