style: Implement ipdl reads without needing default ctors

Differential Revision: https://phabricator.services.mozilla.com/D149743

components/style/values/generics/easing.rs

@@ -21,7 +21,6 @@ use crate::parser::ParserContext;
 )]
 #[value_info(ty = "TIMING_FUNCTION")]
 #[repr(u8, C)]
-/// cbindgen:private-default-tagged-enum-constructor=false
 pub enum TimingFunction<Integer, Number, LinearStops> {
     /// `linear | ease | ease-in | ease-out | ease-in-out`
     Keyword(TimingKeyword),

components/style/values/generics/motion.rs

@@ -73,7 +73,6 @@ pub struct RayFunction<Angle> {
 /// The offset-path value.
 ///
 /// https://drafts.fxtf.org/motion-1/#offset-path-property
-/// cbindgen:private-default-tagged-enum-constructor=false
 #[derive(
     Animate,
     Clone,

components/style/values/generics/position.rs

@@ -67,7 +67,6 @@ pub trait PositionComponent {
 /// A generic type for representing an `Auto | <position>`.
 /// This is used by <offset-anchor> for now.
 /// https://drafts.fxtf.org/motion-1/#offset-anchor-property
-/// cbindgen:private-default-tagged-enum-constructor=false
 #[derive(
     Animate,
     Clone,

components/style/values/generics/transform.rs

@@ -679,7 +679,6 @@ pub fn get_normalized_vector_and_angle<T: Zero>(
 /// A value of the `Rotate` property
 ///
 /// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
-/// cbindgen:private-default-tagged-enum-constructor=false
 pub enum GenericRotate<Number, Angle> {
     /// 'none'
     None,
@@ -772,7 +771,6 @@ where
 /// A value of the `Scale` property
 ///
 /// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
-/// cbindgen:private-default-tagged-enum-constructor=false
 pub enum GenericScale<Number> {
     /// 'none'
     None,
@@ -850,7 +848,6 @@ fn y_axis_and_z_axis_are_zero<LengthPercentage: Zero + ZeroNoPercent, Length: Ze
 /// https://github.com/w3c/csswg-drafts/issues/3305
 ///
 /// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
-/// cbindgen:private-default-tagged-enum-constructor=false
 pub enum GenericTranslate<LengthPercentage, Length>
 where
     LengthPercentage: Zero + ZeroNoPercent,

components/style/values/specified/box.rs

@@ -779,7 +779,6 @@ fn is_default<T: Default + PartialEq>(value: &T) -> bool {
 /// A value for the <single-animation-timeline>.
 ///
 /// https://drafts.csswg.org/css-animations-2/#typedef-single-animation-timeline
-/// cbindgen:private-default-tagged-enum-constructor=false
 #[derive(
     Clone,
     Debug,