nsPromiseConcatenation<CharT>::operator+( const basic_nsAReadableString<CharT>& rhs ) const
operator+( const basic_nsLiteralString<CharT>& lhs, const basic_nsLiteralString<CharT>& rhs )
nsPromiseConcatenation<CharT>::operator+( const basic_nsAReadableString<CharT>& rhs ) const  {    return nsPromiseConcatenation<CharT>(*this, rhs, mFragmentIdentifierMask<<1);  }