Start plumbing connections from the BudgetManager to the BudgetDatabase
This adds the BudgetDatabase as a member of the manager, paving the way
for the switch from using the prefs to store budget to using the proto
database.
This also adds Reserve and Consume entrypoints on the BudgetManager.
Reserve is the entrypoint for the Mojo service to enable Javascript to
purchase reservations with budget. Consume is the entrypoint for clients
of the Manager to determine if an origin should be allowed an action,
either because it has a reservation or because it has enough budget to
cover the cost.
BUG=617971
Review-Url: https://codereview.chromium.org/2272563005
Cr-Commit-Position: refs/heads/master@{#416260}
7 files changed
