style: Update the expected direction vector of rotate property in wpt.

For interpolations with the primitive rotate3d(), the direction vectors of
the transform functions get normalized first. This should also be applied to
rotate property.

https://drafts.csswg.org/css-transforms-2/#interpolation-of-transform-functions

Differential Revision: https://phabricator.services.mozilla.com/D52944

components/style/values/animated/transform.rs

@@ -1249,7 +1249,11 @@ impl Animate for ComputedRotate {
         match (self, other) {
             (&Rotate::None, &Rotate::None) => Ok(Rotate::None),
             (&Rotate::Rotate3D(fx, fy, fz, fa), &Rotate::None) => {
-                // No need to normalize `none`, so animate angle directly.
+                // We always normalize direction vector for rotate3d() first, so we should also
+                // apply the same rule for rotate property. In other words, we promote none into
+                // a 3d rotate, and normalize both direction vector first, and then do
+                // interpolation.
+                let (fx, fy, fz, fa) = transform::get_normalized_vector_and_angle(fx, fy, fz, fa);
                 Ok(Rotate::Rotate3D(
                     fx,
                     fy,
@@ -1258,7 +1262,8 @@ impl Animate for ComputedRotate {
                 ))
             }
             (&Rotate::None, &Rotate::Rotate3D(tx, ty, tz, ta)) => {
-                // No need to normalize `none`, so animate angle directly.
+                // Normalize direction vector first.
+                let (tx, ty, tz, ta) = transform::get_normalized_vector_and_angle(tx, ty, tz, ta);
                 Ok(Rotate::Rotate3D(
                     tx,
                     ty,