When you visited https://localhost previously at some point it not only visited this over a secure channel (https rather than http), it also told your browser, using a special HTTP header: Strict-Transport-Security (often abbreviated to HSTS), that it should ONLY use https for all future visits.
This is a security feature web servers can use to prevent people being downgraded to http (either intentionally or by some evil party).
However if you then then turn off your https server, and just want to browse http you can't (by design - that's the point of this security feature).
HSTS also does prevents you from accepting and skipping past certificate errors.
To reset this, so HSTS is no longer set for localhost, type the following in your Chrome address bar:
chrome://net-internals/#hsts
Where you will be able to delete this setting for "localhost".
You might also want to find out what was setting this to avoid this problem in future!
Note that for other sites (e.g. www.google.com) these are "preloaded" into the Chrome code and so cannot be removed. When you query them at chrome://net-internals/#hsts you will see them listed as static HSTS entries.
And finally note that Google has started preloading HSTS for the entire .dev domain: https://ma.ttias.be/chrome-force-dev-domains-https-via-preloaded-hsts/