Added UMA for usage of BudgetAPI calls.
Although there are metrics for the budget and SES at the time that budget
is consumed, there isn't currently any tracking for which events in the
budget system come via the Budget API interface.
This adds two new metrics, to track queries and reserve requests. It also
adds some basic testing to ensure the metrics are being recorded.
BUG=617971
Review-Url: https://codereview.chromium.org/2524533002
Cr-Commit-Position: refs/heads/master@{#436249}
4 files changed
