operator+( const nsPromiseCConcatenation& lhs, const nsACString& rhs )
operator+( const nsDependentConcatenation& lhs, const nsAString& rhs )
operator+( const nsPromiseCConcatenation& lhs, const nsACString& rhs )  {    return nsPromiseCConcatenation(lhs, rhs, lhs.GetFragmentIdentifierMask()<<1);  }