Basic framework for Budget API.

This implements the basic framework for the Budget API in blink. Only the
getCost and getBudget methods are defined, and a LayoutTest is specified
which checks that the interfaces exist.

BUG=617971

Review-Url: https://codereview.chromium.org/2110833002
Cr-Commit-Position: refs/heads/master@{#410378}
12 files changed