else rv = NS_ERROR_NULL_POINTER;
NS_IMETHODIMP nsWebShell::GetParentURIContentListener(nsIURIContentListener**   aParent){   NS_ENSURE_ARG_POINTER(aParent);  nsresult rv = NS_OK;  if (mParentContentListener)  {    *aParent = mParentContentListener;    NS_ADDREF(*aParent);  }  return rv;}