Something else to consider: this stack may contain SVG animations but not SMIL animations. There might be something to do here with naming or code organization to make it clearer that this is the case / why it is the case.

Indeed, what used to be called Animations are now called AnimationEffects.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ccb91fd6df446c3168d2f24f78749430c5177357

commit ccb91fd6df446c3168d2f24f78749430c5177357
Author: loyso <loyso@chromium.org>
Date: Wed Nov 23 00:53:30 2016

Blink Animation: Rename AnimationStack to EffectStack.

BUG= 624640 

Review-Url: https://codereview.chromium.org/2522823002
Cr-Commit-Position: refs/heads/master@{#434045}

[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/BUILD.gn
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/BUILD.gn
[rename] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/EffectStack.cpp
[rename] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/EffectStack.h
[rename] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/EffectStackTest.cpp
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/ElementAnimations.cpp
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/ElementAnimations.h
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.cpp
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/KeyframeEffectReadOnly.h
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/css/CSSAnimationUpdate.h
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/animation/css/CSSAnimations.cpp
[modify] https://crrev.com/ccb91fd6df446c3168d2f24f78749430c5177357/third_party/WebKit/Source/core/svg/SVGElement.cpp