From the mailing list :

These are the visible changes to the extension system for 3.0.192.x,
which should be coming today or tomorrow.

Breaking Changes

The page_actions.icon property in the manifest has been renamed
page_actions.icons (plural) and is now an array of strings instead of
a single string. This was changed so that page actions could
dynamically change their icon in response to some action in the
browser.
http://src.chromium.org/viewvc/chrom...revision=19772


Other Stuff

We now fire a port.onDisconnect event when the other side of a port closes.
http://src.chromium.org/viewvc/chrom...revision=19686

YAY an onDisconnect.
Perfect. No need for ping timeouts if I was ever gonna get that into the communication.
Haven't used page actions yet but that definitely seems like a good feature.