That's a Google domain, and the numbers represent a specific Chrome extension... in this case, Streak.

I realize it's a Google domain, but not a trusted Google domain.

If you look at do a search for "googleusercontent.com" it shows that it hosted malware and some other nasty stuff.

  http://www.google.com/safebrowsing/diagnostic?site=googleusercontent.com/

If I'm on streak.com and try to login I would like to be authorizing Streak.com

I understand the sentiment, but it can't work that way. What you're authorizing for access is an anonymous unsigned Chrome extension, not the website streak.com. If they allowed the extension to define its own name so that you'd see "streak.com", then you'd see malware masquerading as safe-sounding names in the authorization dialog.