LayerDrawable.setLayerInset () does not work on android 2.3

Question

The following sample works for android 4.1, but for android 2.3 the left and right insert does not change. What is the reason for this behavior?

public class MyFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.badges_fragment_layout, container, false);

    view.setBackgroundDrawable(getCustomDrawable());
    return view;
} 

private Drawable getCustomDrawable() {
    LayerDrawable layerDrawable = new LayerDrawable(new Drawable[]{getBottom(),     getTop()});
    layerDrawable.setLayerInset(1, 5, 0, 5, 0);
    return layerDrawable.mutate();
}

private Drawable getTop() {
    return new ColorDrawable(Color.parseColor("#ffffff"));
}

private Drawable getBottom() {
    return new ColorDrawable(Color.parseColor("#ff0000));
}