/src/main/java/org/htmlunit/html/HtmlElement.java
attributeListeners_.add( listener) ;newNode.attributeListeners_.addAll( attributeListeners_) ;
newNode.attributeListeners_.addAll ( attributeListeners_ ) ;
@Override public DomNode cloneNode(final boolean deep) { final HtmlElement newNode = (HtmlElement) super.cloneNode(deep); if (!deep) { synchronized (attributeListeners_) { newNode.attributeListeners_.clear(); <extra_id_0> } } return newNode; } }