This issue is like http://crbug.com/770307 (Size and Accounting), but only the Accounting part, mostly to get a sense of how much memory it takes in the field.

The browser-side bits are accounted, but they hold only the keys (i.e. not values) for sessionstorage/localstorage (thanks ssid@!).

Not related to known excessive usage, mostly to keep the sizes in check. We could potentially approximate it with leveldb usage, but this may go away as part of leveldb unification .. not sure.

dmurph: WDYT?