It’s easy to find out what Google Chrome’s user-agent is. Using the same trick as I did with the iPhone, I searched for phpinfo HTTP_USER_AGENT in Google Chrome. Click on one of the results and search for HTTP_USER_AGENT on the page. Here’s the image that I see:
My exact user-agent is
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/0.A.B.C Safari/525.13
So “0.2.149.27″ is the current version, but that will change over time. I wouldn’t be surprised if the “525.13″ value for WebKit changed too.
Update: atul points out in the comments that using “about:” or “about:version” in the address bar works well too.
Update: Someone pointed out Google’s official documentation about the Chrome user agent as well.