While sumo is a forked version of XMR, I do not beleive its possible to mine it with your browser. However, plenty of sites have been using the XMR miner and instead of rewarding users with Monero they give out BTC and other coins. Faucethub is a good example of this: 
(tho faucethub doesnt reward in XMR nor sumo unfortunately)
RE: Automine Monero while AFK with just a single Chrome extension: