UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:50.0) Gecko/20100101 Firefox/50.0

Steps to reproduce the problem:
1. open attached index.html in browser
2. change window size
3. reload and repeat

What is the expected behavior?
"bottomline" should always remain visible at bottom of window, page content should always fill window exactly as indicated by height:100% style of html, body & div tags

What went wrong?
"bottomtext" follows when increasing height of window, but not when reducing it
When reloading the page, it fills the window exactly as it should but then again does not reduce its size when the window size is reduced

Did this work before? No 

Does this work in other browsers? Yes

Chrome version: 57.0.2978.0  Channel: n/a
OS Version: OS X 10.12
Flash Version: not installed

This is just one example repro. Attempting to have flex content exactly fill the height of the window leads to all kinds of weird behavior.
The problem also occurs in chromium 53 included with the electron.atom.io project.
 

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