public interface ProvidesResize
RequiresResize.onResize() on its children whenever their size may
 have changed.
 
 
 With limited exceptions (such as RootLayoutPanel), widgets that
 implement this interface will also implement RequiresResize. A typical
 widget will implement RequiresResize.onResize() like this:
 
 
 public void onResize() {
   for (Widget child : getChildren()) {
     if (child instanceof RequiresResize) {
       ((RequiresResize) child).onResize();
     }
   }
 }