In this demo: http://jsbin.com/weqapufoyi/edit?html,css,output

Because span float will automatically wrap, how to make the parent element shrink to the "Expectation" effect.

Can we add a new width/height value(e.g. width: auto-shrink), or already have other solutions?

spec: https://drafts.csswg.org/css-sizing/#width-height-keywords

cc @dholbert @tabatkins @fantasai