aw: Rendering test harness and end-to-end smoke test

The test harness is heavily modelled after LayerTreeTests in
cc.

Add implementation for simulating invalidation and functor
behavior. Add in enough hooks to allow a end-to-end smoke
test from invalidation to draw to functor draw.

BUG=418346

Review URL: https://codereview.chromium.org/786533002

Cr-Commit-Position: refs/heads/master@{#307812}
8 files changed