As an additional security measure, Chrome treats every “file” path as its own origin rather than treating the entire “file” scheme as a single origin (which is what other browsers do). This behavior applies only to “file” URLs and you can force Chrome to revert to a single local origin (like other browsers) by passing the –allow-file-access-from-files switch at startup.
You can find more information on the risks associated with local origins described here: http://blog.chromium.org/2008/12/security-in-depth-local-web-pages.html