I didn't know about it until I looked for another solution to this. The box layout mode is a precursor to [flexbox](https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Flexible_boxes), so it will be replaced eventually, but it is going to be a while by the looks of it. The webkit implementation of the box layout seems quite consistent, however. It worked the same on Android 2.1 and Chromium 25, so I think we can rely on it for quite some time.