UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3088.3 Safari/537.36

Steps to reproduce the problem:
1. Visit http://www.dayah.com/bugs/grid-writing-mode.html
2. "some other content" in second flex cell is overlapped by previous cell's grid with writing-mode text.
3. Resize window. "some other content" snaps into correct location.

What is the expected behavior?
Rendering appears initially as it does after the resize.

What went wrong?
An incorrect initial calculation of the width of a grid with sideways text (writing-mode).

Did this work before? No 

Chrome version: 60.0.3088.3  Channel: dev
OS Version: 10.0
Flash Version: 

http://www.ptable.com/grid/ shows the same problem but in a more complex case.