btn-toolbar - btn-group - content doesn't fit to content on mobile view

Created by: Lausselloic

In alpha.6 btn-toolbar content doesn't wrap to container size.

This example from the doc http://v4-alpha.getbootstrap.com/components/button-group/#button-toolbar Lock the container size and an horizontal scrollbar appear. In alpha.5 btn-toolbar content fits well

Here is the jsfiddle : https://jsfiddle.net/L84dbasj/

Is it due to flexbox, and that component is not rewritten in alpha.6?