Flexbox Gotchas

See https://stackoverflow.com/questions/35049343/chrome-ignoring-flex-basis-in-column-layout

Bottom line, Chrome and Safari resolve percentage heights based on the value of the parent's height property.

Firefox and IE11/Edge use the parent's computed flex height.

Fix attempt #1 at https://jsfiddle.net/medmunds/m7y52379/. It shows the absolute-relative chrome hack.