When current budget is 0, the getBudget will return 2 entries 4 days apart with 0 budgets.

Device:
Nexus 6P, MDB08O, Chrome Beta 60.0.3112.50

Steps:
1) Enable exp web plat features in chrome://flags
2) Visit aluochromium.github.io
3) Set site-engagement to 4 in chrome://site-engagement
4) In page, press "Get Current Budget", allow notifications.
5) Press "Spend Budget" until all budget is gone

Expected:
When budget is 0, getBudget should return 1 BudgetState with 0 budgetat.

Actual:
It is returning 2 with 0, presumably calculating an extra time due to the 4 day expiry.

I've also hit this:

40 at Thu Jul 06 2017 16:45:59 GMT-0700 (PDT)
0 at Mon Jul 10 2017 15:35:42 GMT-0700 (PDT)
-1 at Mon Jul 10 2017 16:45:59 GMT-0700 (PDT)

but have no idea how it got to this state, could be related to this duplicate entry problem though since it looks like an extra round of calculation was made even past 0 budget.