When trying to download Google Chrome, the installer doesn't work and returns an error.
The Google Chrome installer does not support authentication, and that is likely the cause of the problem. When the proxy challenges it to provide authentication credentials, that software doesn't know how to provide the right information, so it fails to continue with the installation. The solution to this is to disable authentication for that software, which can be done by adding the following 3 lines of code in the local policy file:
request.header.User-Agent="Google Update" url.domain="google.com" Authenticate(no) Allow
request.header.User-Agent="Microsoft BITS" url.domain="google.com" Authenticate(no) Allow
That will both disable authentication and allow connections from the Google installer and only when going to google.com. When the deployment of Google Chrome is complete, the code may be removed or left in place.