I think this is very clever. Assuming this is something to do with recruitment (as the other comments suggest), then of course I find it intensely irritating and it confirms my pre-existing notion that I would never want to work for a company like Google. But, on the other hand, the people who devised this puzzle are clearly people who would be enticed by a puzzle like it, and would therefore think it was a good way…
No puzzle here. You can only log in if Google has flagged your search topics. On google search, you have the variable window.location.search = "?gfe_rd=cr&ei=XXXGyZiVNHoFcuF8Qe7wYHACw&gws_rd=ssl" That string is appended to the url of the iframe: src=" https://foobar.withgoogle.com/"+window.location.search
The code snippet will only load the URL with appended values if there are present in the parent URL: e.g. https://www.google.com/foobar/?some_query_string