Make sure oauth popup windows get closed

[durka]

Samuel Cole reported on Slack that Safari was reloading the popup in a background tab but keeping it in the background, making it seem like nothing was happening. The popup should close as soon as it finishes redirecting, AFAIK. But maybe there's a way to give it a unique name or something, just in case, so it doesn't go back to a previous tab.

[dglazkov]

I think this should work now -- we changed the flow altogether.

[durka]

@samuelcole can you still repro?