It worked for me with chromium-bin-5.0.308.0_p37385 on 64-bit Gentoo.
The one thing I had to do (besides launching it as 'chromium-bin --no-sandbox --enable-webgl', as you mentioned) was to create a symbolic link from /usr/lib/libGL.so to /usr/lib/libGL.so.1 .
Has anybody sucessfully ran the demos?