The upstream spec has removed the timing objects (https://github.com/w3c/csswg-drafts/pull/2432 ); we should follow suit.
Summary of relevant changes:
* Replaced the timing member of AnimationEffectReadOnly with the getTiming() and updateTiming() methods on AnimationEffect.
* Removed the AnimationEffectTimingReadOnly and AnimationEffectTiming interfaces.
* Renamed the AnimationEffectTimingProperties dictionary to EffectTiming.
* Renamed the ComputedTimingProperties dictionary to ComputedEffectTiming.
* Introduced the OptionalEffectTiming dictionary for use with the updateTiming() method.
Comment 1 by smcgruer@chromium.org
, Mar 20 2018