We introduced a primitive implementation of getAnimations() on Document and Element with https://bugs.webkit.org/show_bug.cgi?id=179535, but we need to implement the finer aspects of those methods to match the spec, specifically the order of returned animations and filtering for animations that are current or in effect. See https://w3c.github.io/web-animations/#dom-document-getanimations and https://w3c.github.io/web-animations/#dom-animatable-getanimations.
This has been done across a variety of commits.