UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2695.1 Safari/537.36

Steps to reproduce the problem:
1. Create a div with display: flex and justify-content set to anything other than flex-start
2. Place some divs inside it all with same percent width (if flex-flow:row) or percent height (if column) without overflowing
3. Compare the offsetWidth (if rows) or offsetHeight (if columns) of the children elements

What is the expected behavior?
The offsetWidth (if rows) or offsetHeight (if columns) for all of the children elements should be the same due to them having the same percentage. Getting the width or height using getComputedStyle works this way.

What went wrong?
The offsetWidth or offsetHeight values are often not the same despite the equal percent width/height values. They do sometimes match under seemingly-random circumstances (see comments).

Did this work before? N/A 

Chrome version: 51.0.2695.1  Channel: canary
OS Version: 10.0
Flash Version: Shockwave Flash 21.0 r0

Example/testing for height: http://codepen.io/justinm53/full/grxQNE/

- Only under some combinations of parent height and justify-content value do the heights in this example match.
- Only seems to happen with justify-content being changed from flex-start (default).