PNaCL port of bomberclone - www.bomberclone.de. GPLv2. Source: http://github.com/tapted/bomberclone-nacl
Multiplayer still a work in progress - YMMV. To try it, you will likely need to enable "NaCl Socket API" in chrome://flags and use the Chrome dev channel. However, a crash currently seems likely unless loading the extension unpacked in developer mode.