I don't think a XULRunner-like environment has ever been on the Chrome roadmap though. Chrome's been pretty consistent in its intention to expose only v8 + webkit as its extension and app environment, although things like native client are blurring this somewhat.
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Apps using browser as runtime environment, they may or may not be web-apps itself. See XULRunner. And http://pencil.evolus.vn for example.
I don't think a XULRunner-like environment has ever been on the Chrome roadmap though. Chrome's been pretty consistent in its intention to expose only v8 + webkit as its extension and app environment, although things like native client are blurring this somewhat.