surface: add missing va_marshaller for layout signal
I saw this coming across through a ffi boundary in Sysprof, and we wanted to keep most things within GDK using native marshalling to improve profiler results when frame pointers are not used.
I saw this coming across through a ffi boundary in Sysprof, and we wanted to keep most things within GDK using native marshalling to improve profiler results when frame pointers are not used.