Auto merge of #27032 - mrobinson:fractional-iteration, r=jdm

animations: Finish support for fractional iteration counts

This change also improves support for creating animations with negative
delays, as that is necessary to test support for fractional iteration
lengths.

Fixes: #14858

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---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #14858
- [x] There are tests for these changes

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components/style/values/generics/easing.rs

@@ -6,7 +6,6 @@
 //! https://drafts.csswg.org/css-easing/#timing-functions
 
 use crate::parser::ParserContext;
-use crate::values::CSSFloat;
 
 /// A generic easing function.
 #[derive(
@@ -118,18 +117,3 @@ impl<Integer, Number> TimingFunction<Integer, Number> {
         TimingFunction::Keyword(TimingKeyword::Ease)
     }
 }
-
-impl TimingKeyword {
-    /// Returns the keyword as a quadruplet of Bezier point coordinates
-    /// `(x1, y1, x2, y2)`.
-    #[inline]
-    pub fn to_bezier(self) -> (CSSFloat, CSSFloat, CSSFloat, CSSFloat) {
-        match self {
-            TimingKeyword::Linear => (0., 0., 1., 1.),
-            TimingKeyword::Ease => (0.25, 0.1, 0.25, 1.),
-            TimingKeyword::EaseIn => (0.42, 0., 1., 1.),
-            TimingKeyword::EaseOut => (0., 0., 0.58, 1.),
-            TimingKeyword::EaseInOut => (0.42, 0., 0.58, 1.),
-        }
-    }
-}