broken fonts in scratch-paint playground

[kccuber-scratch]

Expected Behavior

Please describe what should happen
The paint editor fonts should show up in the playground.

Actual Behavior

Describe what actually happens
All the fonts are serif.

Steps to Reproduce

Explain what someone needs to do in order to see what's described in Actual behavior above

Steps to reproduce the behavior:

1. Go to 'https://llk.github.io/scratch-paint/' (or clone the repository and build it, and start the playground)
2. Click on the text tool
3. Click the font dropdown
4. See error

System Details

If the problem occurs in the browser, please provide operating system and browser e.g. Mac OS 10.11.6 Safari 10.0
Happens in Firefox on Windows 10

Screenshots
If applicable, add screenshots to help explain your problem.

I think this is caused by #1514 because that only makes fonts work if paint is linked to the GUI