Fixup prepends "http://" if the user types a URL without a scheme.  Now that we're switching to "hide HTTPS schemes by default, show HTTP", I think the time is right to consider changing this to prepend https:// by default; that is, if you want http://, you have to type it explicitly.

If we did this, we would also want to change the machinery that re-shows a scheme in the omnibox to only re-show HTTP schemes, not HTTPS ones.  This would reduce the shifting of text when editing the omnibox.  It's basically the "hide HTTP scheme" changes of years back, except for HTTPS instead now that that's the "new normal".

There may be considerations here with how the HUP orders search prefixes; whether we need to add some kind of fallback to HTTP if HTTPS fails hard; and potentially other stuff.