Even as native applications transition to the cloud there are some things one is bound to miss about them, whether it is the pinging sound when you get a new message, or their ability to collapse quietly into the system tray, running the background till something comes up that need your attention. Google aims to bringthese features to web applications as well.
Now these privileges are available to all applications. Web applications such as Facebook and Twitter can now persist their state, and continue to give you notifications of updates even when their window is closed. Now such applications can continue running even when all windows are closed!
This can has a number of uses even besides notifications. Applications such as Dropbox, could possibly now provide basic cross-platform syncing support even without a native application! Imagine setting a YouTube video to upload and closing the browser window as the upload continues in the background. You could close the window of you chat application while still being online in the background and continuing to receive chat requests and messages. Such thing and more could be made possible with this new API.
It will be interesting to see how these features will be used by applications in the future, however it is also worrying that these are non-standard features are limited to Chrome only. Google continues to tout its support for new open web standards, however implementing browser-specific features to give Chrome an edge doesn't seem like what's best for the open web.