I updated google chrome from the software updates in ubuntu 12.04 , but it didn't actually update . The "about google chrome " is still showing the previous release .
Download the latest deb.
Install it.It will add repository to your software source. After that you can update it via terminal when a update pack release. via comand
If you would like to keep you browser up to date, I think the easiest thing to do is to add the PPA. I will explain how to do this for both Chrome and Chromium. These two browsers are mostly the same, but you can check out the differences here.
First you have to install the key. This can be done by opening Terminal and typing
Step two is to add the repository
Then you update and, if you haven't already, install Google Chrome
Chromium is more straight forward. Just add the PPA, update, and install by typing this in Terminal: