When <base href> is present, history.replaceState and
history.pushState behave inconsistent with relative URLs.
http://code.google.com/p/chromium/issues/detail?id=274024
Contrary to what one expect, passing '' as the URL parameter to
replaceState/pushState does not associate the currently active
URL with the history entry, but a path relative to <base href>.
To fix the issue, explicitly associate the current active URL
with the history's state.
