*aParent = nsnull;
DOMCSSDeclarationImpl::GetParent(nsISupports **aParent){  if (nsnull != mRule) {    return mRule->QueryInterface(kISupportsIID, (void **)aParent);  } else {    NS_ENSURE_ARG_POINTER(aParent);    *aParent = nsnull;  }  return NS_OK;}