Does Chrome auto-complete rely on history? If so, periodically scripting a purge on the history file [1] may selectively gimp your autocomplete as required. Downside, you lose your history - won't find that great tip/info you found but didn't bother to bookmark.

Personally, I like tools that prevent me from resolving HN/reddit/etc during "vulnerable" (afternoon) hours.

[1] https://superuser.com/questions/480646/how-can-i-delete-all-...