In my testing, a looping compute shader was enough to crash the tab on its own, but it needed waiting render shaders to crash the WindowServer.

Interestingly though there was another way to make only the tab crash, even if I had all three shaders in the pipeline: If I placed the canvas far offscreen using position: absolute, only the tab would crash even if the render shaders were waiting! There's some weird interactions going on I don't yet fully understand.