[OT] Google's historyFrame

Does anyone know how the Google services historyFrame works? If you
Google’s services that make extensive use of AJAX (for example, Google
Calendar), you’ll eventually come across a hidden iframe called the
historyFrame. This frame enables the user to use the back and forward
buttons even though the site is primarily AJAX based. All it contains is

Trying to find parent._goHist() in the deliberate maze of Google’s page
source is a bit more difficult. I’m wondering if anyone’s already done
written anything similar, or reckons they can have a pretty good guess
what it contains.