Fix HistoryLocation test for static site testing.

Before this change this test fails when running tests under a static
site (aka 'file://some/path/index.html').

I am not 100% sure that this is the correct way to fix this issue, but
tests pass under both scenarios with this change (static and `rackup`
tests).

Thanks to @alexspeller for pointing me in the right direction to start
tracking this issue down.