Force any pending property changes to synchronously deliver to handlers
specified in the observe
object.
Note: normally changes are processed at microtask time.
// Dart note: had to rename this to avoid colliding with
// Observable.deliverChanges. Even worse, super calls aren't possible or
// it prevents Polymer from being a mixin, so we can't override it even if
// we wanted to.
void deliverPropertyChanges() {
if (_propertyObserver != null) {
_propertyObserver.deliver();
}
}