message: Started when attached to window
  Doesn't seem right to put in onLayout because that can be calleed multiple times?
diff: @@ -178,6 +178,12 @@ public class NavigationStackView extends ViewGroup {
  return sceneItems.get(sceneKeys.get(index)).view;
  }
  + @Override
  + protected void onAttachedToWindow() {
  + super.onAttachedToWindow();
  + onAfterUpdateTransaction();
  + }
  +
  @Override
  public void onDetachedFromWindow() {
  if (keys.size() > 0) {
  @@ -232,7 +238,6 @@ public class NavigationStackView extends ViewGroup {
  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
  - onAfterUpdateTransaction();
  }
  static class SceneItem {
  