with that little programs you can update and downgrade your portable Chrome / Chromium.
switching between different versions: dev/beta/release
http://www.paehl.de/news/page_id=177
or
http://stadt-bremerhaven.de/portable-google-chrome-8
(inside the portable chrome download package)

place the updater.exe one folder level higher than your chrome.exe (not portable chrome starter.exe)
make your try with a copy of your chrome.