nsProperties::UndefineProperty(const char* prop)
nsPersistentProperties::UndefineProperty(const char* prop)
nsProperties::UndefineProperty(const char* prop){    nsCStringKey key(prop);    if (!Exists(&key))        return NS_ERROR_FAILURE;    nsISupports* prevValue = (nsISupports*)Remove(&key);    NS_IF_RELEASE(prevValue);    return NS_OK;}