I believe it's available in later 7 builds and all dev channel builds after that. Note that it is not yet available in the beta or stable channel builds (since we're still perfecting it).

Also, I really recommend you upgrade your Chromium version! I believe security updates are only back-ported to the current stable release, which means you haven't gotten any such updates for a while! (Stable is now at 8.)

Works on Mac OS with Chromium 10.0.601.0 (68155)

Chrome 8.0.552.215 also works on Mac.