We currently fail the following test because the onfinish event fires before the finished promise resolves:

external/wpt/web-animations/interfaces/Animation/onfinish.html
  - onfinish event is fired when the currentTime < 0 and the playbackRate < 0

I am not 100% on this, but from the spec (https://w3c.github.io/web-animations/#update-an-animations-finished-state) it appears like one should resolve the promise first (which is what the test expects):

"The procedure to update an animation’s finished state for animation ... is as follows:
...
5. If current finished state is true and the current finished promise is not yet resolved, perform the following steps:

  1. Let finish notification steps refer to the following procedure:

    1. If animation’s play state is not equal to finished, abort these steps.
    2. Resolve animation’s current finished promise object with animation.
    3. Queue a task to fire a finish event at animation. The task source for this task is the DOM manipulation task source.

  2. If synchronously notify is true, cancel any queued microtask to run the finish notification steps for this animation, and run the finish notification steps immediately.

  3. Otherwise, if synchronously notify is false, queue a microtask to run finish notification steps for animation unless there is already a microtask queued to run those steps for animation.
"

Whether 'synchronously notify' is true or false, it appears that the promise should resolve before the event. Our code does not currently do this:

[97710:97744:1005/095145.898140:10879385613997:INFO:Animation.cpp(963)] Enqueueing pending_finished_event_
[97710:97744:1005/095145.898223:10879385614077:INFO:Animation.cpp(1145)] Resolving finished promise (maybe async)
[97710:97744:1005/095145.898246:10879385614099:INFO:Animation.cpp(1239)] Animation::ResolvePromiseMaybeAsync, resolve promise without posting
[97710:97744:1005/095145.898298:10879385614152:INFO:ScriptedAnimationController.cpp(116)] Dispatching "finish" to "AnimationPlayer"
[97710:97710:1005/095145.942713:10879385658570:INFO:CONSOLE(24)] "animation.onfinish fired", source: file:///usr/local/google/home/smcgruer/chromium/src/third_party/WebKit/LayoutTests/external/wpt/web-animations/interfaces/Animation/onfinish.html (24)
[97710:97710:1005/095145.942888:10879385658741:INFO:CONSOLE(19)] "animation.finished fired", source: file:///usr/local/google/home/smcgruer/chromium/src/third_party/WebKit/LayoutTests/external/wpt/web-animations/interfaces/Animation/onfinish.html (19)

It is interesting to me that it *looks* from the C++ side like we are resolving the promise first before dispatching finish, but the javascript definitely sees them the other way around.