The functionality can be exposed on any webpage. It's likely that Google is only allowing it via the Web App Store for further vulnerability testing and moderation ability over the Web Store Content.
about:flags and two clicks will enable NaCl TCP/UDP sockets and a third click will enable NaCl on any webpage with a prudent and applicable warning about the potential security risk.
about:flags and two clicks will enable NaCl TCP/UDP sockets and a third click will enable NaCl on any webpage with a prudent and applicable warning about the potential security risk.