NS_IMETHOD ContentReplaced(nsIDocument *aDocument, nsIContent* aContainer, nsIContent* aOldChild, nsIContent* aNewChild, PRInt32 aIndexInContainer) { return NS_OK; }
NS_IMPL_NSIDOCUMENTOBSERVER_CONTENT(HTMLContentSink)
  NS_IMETHOD ContentReplaced(nsIDocument *aDocument, nsIContent* aContainer,                             nsIContent* aOldChild, nsIContent* aNewChild,                             PRInt32 aIndexInContainer)  {    return NS_OK;  }