Animation and clamping of width, height, and size #12645
Description
As per #3340 (comment) there is a reason to have negative opacity Keyframe values, namely additive animation.
Width and height behave differently. Values are clamped to disallow negative values. The same reason to allow negative opacity values applies to width and height.
The introduction of a size shorthand for width and height offers a unique and exciting opportunity to correct this discrepancy going forward. #820
The following CodePen shows expected behavior for translation and opacity but failure of width and height, when using manually constructed Web-Animations. This would apply to additive CSS Animations as well. https://codepen.io/kvndy/pen/dPYKYov
Please allow negative width and height values for the size shorthand in the creation of Keyframes. Thanks.