[OT] Google's historyFrame

Does anyone know how the Google services historyFrame works? If you
Firebug
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
this:

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
it,
written anything similar, or reckons they can have a pretty good guess
at
what it contains.
-Nathan