Besides Air, there was Mozilla's Prism/WebRunner/Chromeless, Fluid for OSX and several others. What advantage does Chrome Apps have other those previous failures?
Mozilla's Prism/WebRunner/Chromeless are all basically defunct, and Chrome Apps aren't really the same as those anyway. Chrome Apps and Firefox OS Apps are basically the same – and in both cases it's adding some extra APIs that web pages can't normally get access too, and an optional packaging format, and a little application-related metadata. Firefox Apps are a bit more cross-platform, as they look a bit more like native apps on normal desktop systems and on Android.
