nsIDOMStorageManager Interface

 Clear keys owned by offline applications.  All data owned by a domain
 with the "offline-app" permission will be removed from the database.

void clearOfflineApps()

 Returns instance of localStorage object for aURI's origin.
 This method ensures there is always only a single instance
 for a single origin.

nsIDOMStorage2 getLocalStorageForPrincipal(in nsIPrincipal aPrincipal)

 Return the amount of disk space used by a domain.  Usage is checked
 against the domain of the page that set the key (the owner domain), not
 the domain of the storage object.

 @param aOwnerDomain The domain to check.
 @returns the space usage of the domain, in bytes.

long getUsage(in AString aOwnerDomain)