If you install Oh My Zsh on Chrome OS and use the Agnoster theme, the fonts won't display correctly, as some of the symbols are missing. This is true even if you install the powerline fonts in termina. This can be fixed by specifying a user css font.
In termina, press CTRL -> Shift -> P to open the Secure Shell App Profile Settings. Under
Custom CSS (URI) enter
Text Font Family specify the font you'd wish to include, i.e.
"Hack","DejaVu Sans Mono".
And now you should have a pretty prompt: