[PATCH 2 of 2] ui: add explicit path to write prompt text bypassing buffers

[Augie Fackler]

> On Feb 5, 2018, at 13:11, Yuya Nishihara <yuya at tcha.org> wrote:
> 
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1517831331 -32400
> #      Mon Feb 05 20:48:51 2018 +0900
> # Node ID 59869758acd7b38d9de045d5a72f5196cc80f047
> # Parent  9be8a0f8d48502734066a66e3d5b9b22e460ae70
> ui: add explicit path to write prompt text bypassing buffers

queued, thanks