For <a href="http:&#x2F;&#x2F;Clara.io" rel="nofollow">http:&#x2F;&#x2F;Clara.io</a>, we explored a bunch of headless gl solutions and none worked.  It may have changed by now.  But even if you got a headless gl solution working, it likely would have poor extension support, which means the results will suffer anyhow. :(