This glitch page fails to render properly

[speigg]

I have this page on glitch.com which servo is not able to display properly (using the latest nightly for macOS)

https://glitch.com/~servo-web-layer-gl

This page is supposed to rasterize a DOM element using html2canvas, then render that texture in WebGL using three.js. I'm not sure where exactly in the pipeline things are breaking down, and not sure how to work with servo beyond the errors that are output in the terminal.

Note: I had to attach a dummy SVGElement global to the window object in order to avoid errors like these:
01Z ERROR script::dom::bindings::error] Error at https://three-web-layer.glitch.me/script.96a3883c.js:34350:30 invalid 'instanceof' operand getWindowOf(...).SVGElement