The simpliest way to do it is to use CancelableCallback. You should check the first action is complete and then call the second:
mMap.animateCamera(CameraUpdateFactory.newLatLngBounds(bounds, size.x, height, 0), new CancelableCallback() {
@Override
public void onFinish() {
CameraUpdate cu_scroll = CameraUpdateFactory.scrollBy(0, 500);
mMap.animateCamera(cu_scroll);
}
@Override
public void onCancel() {
}
});