The spec [1] says: > When translate, rotate or scale are animating or transitioning, > and the from value or to value (but not both) is none, the > value none is replaced by the equivalent identity value > (0px for translate, 0deg for rotate, 1 for scale). This means we shouldn't convert the `none` into the identity value if both from value and to value are `none`. (I guess this may affect the creation of stacking context during animation?). The related wpt is [2]. [1] https://drafts.csswg.org/css-transforms-2/#valdef-translate-none [2] https://searchfox.org/mozilla-central/rev/b096dcf0ea226af628fe03f7e7acb56a25853533/testing/web-platform/tests/css/css-transforms/animation/translate-interpolation.html#64-75

It shouldn't affect the stacking context during animation. So long as there is a scheduled, running, or filling animation, there should be a stacking context as per: "While an animation is applied but has not finished, or has finished but has an animation-fill-mode of forwards or both, the user agent must act as if the will-change property ([css-will-change-1]) on the element additionally includes all the properties animated by the animation."[1] and: "For every property targeted by at least one animation effect that is current or in effect, the user agent must act as if the will-change property ([css-will-change-1]) on the target element includes the property."[2] [1] https://drafts.csswg.org/css-animations/#animations [2] https://drafts.csswg.org/web-animations-1/#side-effects-section

It both from value and to value are none, we don't have to convert it into identity value, so just return None. We have done this for translate and scale in other bugs.

So we can drop a lot of code. Depends on D11247

Rotate accepts rotate axis and angle in any order (i.e. <number>{3} <angle> or <angle> <number>{3}), so we rewrite the parser.

Pushed by boris.chiou@gmail.com: https://hg.mozilla.org/integration/autoland/rev/f94bba680dc2 Part 1: Rewrite the interpolation of Rotate to return correct type. r=birtles https://hg.mozilla.org/integration/autoland/rev/3bd1f4cc8f9e Part 2: Serialize Rotate by servo. r=emilio https://hg.mozilla.org/integration/autoland/rev/36e5bf9afd50 Part 3: Parse any order of number and angle for Rotate. r=emilio

https://hg.mozilla.org/mozilla-central/rev/f94bba680dc2 https://hg.mozilla.org/mozilla-central/rev/3bd1f4cc8f9e https://hg.mozilla.org/mozilla-central/rev/36e5bf9afd50