Can you convert this doodle GIF into lossless WebM? It would be interesting to see the numbers. I assume lossy compression would look bad, probably not worth it.

Lossy wouldn't look bad, it's just not a direct comparison :) Here are 3 files: a lossless WebP and two lossy ones with max and min quality settings https://www.dropbox.com/sh/q1jqoru5ljtq9on/P2ELh8NkA6?lst The lossless one is slightly bigger than the GIF which I did not expect. The high-quality lossy one is obviously overkill and is huge! The low-quality lossy one is smaller but looks like crap.

  GIF:     81 kB
  WebP:    82 kB
  -q 0:    59 kB
  -q 100: 259 kB

Yeah, that's what I would expect from WebP, as I played with gif2webp before, but I thought you said WebM, as in proper video?

Well... I don't know how to make a lossless WebM video. And according to the bottom of this page https://developers.google.com/speed/webp/faq it would probably be bigger anyway.