nsresult rv;  nsCOMPtr<nsIPrefBranch> prefBranch = do_QueryInterface(mPrefService, &rv); if (NS_SUCCEEDED(rv)) rv = prefBranch->ClearUserPref(aPrefName); return rv;
if (NS_FAILED(SecurePrefCheck(pref_name))) return NS_ERROR_FAILURE; return _convertRes(PREF_ClearUserPref(pref_name));
NS_IMETHODIMP nsPref::ClearUserPref(const char *aPrefName){  nsresult rv;  nsCOMPtr<nsIPrefBranch> prefBranch = do_QueryInterface(mPrefService, &rv);  if (NS_SUCCEEDED(rv))    rv = prefBranch->ClearUserPref(aPrefName);  return rv;}