[worklets] Introduce AnimationWorkletGlobalScope and ThreadedWorkletGlobalScope
The ThreadedWorkletGlobalScope is simpler than a WorkerGlobalScope as
- It doesn't need to report exceptions to the main thread they can just be logged to the console.
AnimationWorkletGlobalScope doesn't have anything on it at the moment, but is used in the AnimationWorkletThreadTest (which is a clone of the CompositorWorkerThreadTest).
BUG=
567358
Committed:
https://crrev.com/dbc47ca435e2b5aba33485cbd62a75dd3683b622
Cr-Commit-Position: refs/heads/master@{#414517}