UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.75 Safari/537.36

Steps to reproduce the problem:
There may be more minimal ways to repro, but this is what's doing it for me
0. Use an app that's based on hterm, like mosh or secure shell
https://chrome.google.com/webstore/detail/mosh/ooiklbnjmhbcgemelgfhaeaocllobloj?hl=en
https://chrome.google.com/webstore/detail/secure-shell/pnhechapfaindjhompbnflcldabbghjo?hl=en
1. Use zsh with the powerlevel9k theme (https://github.com/bhilburn/powerlevel9k)
2. run tmux
3. split the window vertically
4. hit enter a few times on the left prompt

What is the expected behavior?
vertical split from tmux is one continuous line

What went wrong?
vertical split appears jagged (see screenshot)

WebStore page: https://chrome.google.com/webstore/detail/mosh/ooiklbnjmhbcgemelgfhaeaocllobloj?hl=en

Did this work before? N/A 

Chrome version: 62.0.3202.75  Channel: n/a
OS Version: 10.0
Flash Version: 

I initially reporting this to the app developer here: https://github.com/rpwoodbu/mosh-chrome/issues/163
 

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