This test resizes the stream by updating the PipeWire stream properties.
This triggers a format negotiation, that results in the buffers being
reallocated with the new size. The test makes sure we eventually
receive this new size.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2270>
Tests that creating and starting a virtual screen cast monitor works,
and that at least one one buffer is processed.
Currently the content of the buffer isn't checked more than it can be
mmap():ed. Only MemFd buffers are tested for for now, as DMA buffers
would need a surfaceless EGL context to check properly.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>