Auto merge of #18210 - mantaroh:clip-interpolation-fix, r=nox

Skip adding/accumulating ClipRect values which corresponding rect offset is auto.

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This is a PR for https://bugzilla.mozilla.org/show_bug.cgi?id=1390352

This patch will skip adding/accumulating the values which corresponding rect offset is auto, and  make Servo_AnimationValues_ComputeDistance return negative value instead of 0.0 when the function fails to distinguish its failure.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

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There are already these tests in dom/smil/tests of gecko, this PR will enable these tests.
For detail, see https://bugzilla.mozilla.org/show_bug.cgi?id=1390352.

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components/style/properties/helpers/animated_properties.mako.rs

@@ -924,6 +924,27 @@ impl Into<FontStretch> for f64 {
 impl<H, V> RepeatableListAnimatable for generic_position::Position<H, V>
     where H: RepeatableListAnimatable, V: RepeatableListAnimatable {}
 
+/// https://drafts.csswg.org/css-transitions/#animtype-rect
+impl Animate for ClipRect {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let animate_component = |this: &Option<Au>, other: &Option<Au>| {
+            match (this.animate(other, procedure)?, procedure) {
+                (None, Procedure::Interpolate { .. }) => Ok(None),
+                (None, _) => Err(()),
+                (result, _) => Ok(result),
+            }
+        };
+
+        Ok(ClipRect {
+            top:    animate_component(&self.top, &other.top)?,
+            right:  animate_component(&self.right, &other.right)?,
+            bottom: animate_component(&self.bottom, &other.bottom)?,
+            left:   animate_component(&self.left, &other.left)?,
+        })
+    }
+}
+
 impl ToAnimatedZero for ClipRect {
     #[inline]
     fn to_animated_zero(&self) -> Result<Self, ()> { Err(()) }

components/style/values/computed/mod.rs

@@ -445,7 +445,7 @@ pub type NonNegativeLengthOrPercentageOrNumber = Either<NonNegativeNumber, NonNe
 
 #[allow(missing_docs)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
-#[derive(Animate, Clone, ComputeSquaredDistance, Copy, Debug, Eq, PartialEq)]
+#[derive(Clone, ComputeSquaredDistance, Copy, Debug, Eq, PartialEq)]
 /// A computed cliprect for clip and image-region
 pub struct ClipRect {
     pub top: Option<Au>,