This extension is meant to create more native Webkit notifications on Linux Operating Systems which use the notify-osd notification framework. Notify-OSD is installed on Ubuntu by default and used for all system notifications. This is a first release which does not support HTML5 notifications (but will in next release, view LaunchPad project page)
However, Chrome is not able to access anything on the desktop that would allow you to be able to display these notifications WITHOUT using NPAPI (http://code.google.com/chrome/extensions/npapi.html) As a result this plugin uses a very big hammer in a very small way. The entire extension is open source and you can view the source for the NPAPI on the project page.
You can download and install chromify-osd from here