You're going back to 4.8, because avast 5.0 didn't offer Chrome, that is probably the best laugh I have had for a while.
If avast was to install Chrome without your knowledge people would be hopping mad. I installed the original release of avast 5.0 over 4.8 and it most certainly offered Chrome, which I declined as I don't rate it that highly. So I don't really know why your install didn't, but we don't know what you did, clean install or update or what avast version it was, current version is 5.0.396.