@Override
  public synchronized void onTransformChanged(Matrix transform) {
    for (ZoomableController.Listener listener : mListeners) {
      listener.onTransformChanged(transform);
    }
  }
An implementation of {@link ZoomableController.Listener} that allows multiple child listeners to
be added and notified about {@link ZoomableController} events.
samples/zoomable/src/main/java/com/facebook/samples/zoomable/MultiZoomableControllerListener.java