If I'm reading the sample implementation[0] correctly, the update mechanism isn't Omaha[1] (aka Google Update), but the CRX extension update mechanism[2] that keeps extensions and app bundles up to date.
Omaha is a service which we ask questions like: "I've got version $x of $foo, what should I do?". We use it for extensions as well as the main browser update.
The CRLSet is packaged as an extension (it's actually a .crx), but with a custom install callback that delta updates the current version.
The CRLSet is packaged as an extension (it's actually a .crx), but with a custom install callback that delta updates the current version.