Default or custom installation. Win XP, Vista, W7, or 8. Clean install or upgrade (within the program). Avast! always shows the window where it offers Google Toolbar and Chrome. If it is a clean install, it shows it at the beggining. See screenshot ( It is in Spanish because I am in S.A. ). If it is an upgrade, after reboot (Sorry don't have an image for it).
If it does not show it, something was not right with the install and it is better to either reinstall Avast! or run an Avast! Repair.