Implement current location lookup as can.compute for import redirect. #60873704

Per [story 60873704](https://www.pivotaltracker.com/story/show/60873704).  Also solves bugs [61653504](https://www.pivotaltracker.com/story/show/61653504) and [62162178](https://www.pivotaltracker.com/story/show/62162178).