if (!aAttrName) return PR_FALSE;
if (mMapped && mMapped->HasAttribute(aAttrName)) return PR_TRUE;
nsHTMLMappedAttributes::HasAttribute(nsIAtom* aAttrName) const{  if (!aAttrName)    return PR_FALSE;  const HTMLAttribute* attr = HTMLAttribute::FindHTMLAttribute(aAttrName, &mFirst);  return attr != nsnull;}