Android and Windows are supporting inline reply for web notifications (Issue 599859). And now it's time to start implementing it for Chrome OS.
I think most of non-UI code are already implemented by their works, so what we do is implementing native UI for Chrome OS Message Center. We already support inline reply for ARC notification so we don't expect much works except UI (eg. forcusing, keyboard, IME ..., etc). But some tweak might be necessary.
The UX work is filed separately: Issue 773585
Comment 1 by yoshiki@chromium.org
, Oct 11 2017