When the assign(url)
method is invoked, the UA must resolve the argument, relative
to the API base URL specified by the entry settings object, and if that
is successful, must navigate the browsing
context to the specified url, with exceptions enabled.
When the replace(url) method is invoked, the UA must resolve the argument, relative to the API base URL specified by the
entry settings object, and if that is successful, navigate the browsing context to the specified url with replacement enabled and exceptions enabled.