Intent to prototype and ship: AnimationFrameProvider for DedicatedWorkerGlobalScope

[Andrew Osmond]

Summary: Implementing AnimationFrameProvider will allow dedicated worker threads to access requestAnimationFrame and cancelAnimationFrame to drive worker based animations. This is a typical way to drive OffscreenCanvas rendering, and as such is a dependency for that to eventually ship.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1738971

Standard: https://html.spec.whatwg.org/multipage/imagebitmap-and-animations.html#animation-frames

Platform coverage: all

Preference: No preference.

Other browsers: Chrome has shipped it since 69.

web-platform-tests:

https://searchfox.org/mozilla-central/source/testing/web-platform/tests/html/dom/idlharness.worker.js

https://searchfox.org/mozilla-central/source/testing/web-platform/tests/workers/WorkerGlobalScope_requestAnimationFrame.tentative.worker.js