See  issue 802027  for some context, but basically:

* We currently surface the "Free disk space for the profile directory" number on chrome://quota-internals

* Circa 58, we don't actually use that number as the primary factor for the size of the pool.

We should surface at least:

* Size of disk
* Amount free
* Temp pool calculation result
* Per-origin result

And probably have incognito-specific results too, since those calculations differ.