In Safari Technology Preview, and the Webkit Nightly Build, on element with `display: flex; flex-wrap: wrap;` and an explicit height, the child do not stretch to fit the height of the container, as would be expected with `align-items: stretch; align-content: stretch`. Rather, they stretch to the height of the tallest sibling on the same row. Safari 10.0, Firefox 49.0.1, and Chrome 54 all exhibit the correct, expected behaviour. An example of this can be found here: http://codepen.io/anon/pen/PGaZyP
<rdar://problem/28825468>
This was fixed in https://trac.webkit.org/changeset/207535. *** This bug has been marked as a duplicate of bug 163572 ***