During interactive resizes, we progressively change the size of the
client surface and send config events with these sizes to the client.
After that, the toplevel->pending.size keeps the size of the last config
event that we've sent, i.e. the surface size after the resize is over.
Later, if the client spontaneously resize (by attaching a buffer with a
different size or setting the viewport destination, for instance), their
surface size will change, but toplevel->pending.size continues being
that old size from after the resize. If something happens and Weston
decides to send a config event, clients may re-allocate to that old
size, resulting in a sudden resize.
This does not happen when a client goes from fullscreen/maximized to
windowed mode because in such cases we are resetting
toplevel->pending.size to zero. So in the next config event that clients
receive they are allowed to attach buffers with the size that they
prefer.
So do the same after a resize: set the pending config size to zero.
Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>