Auto merge of #18305 - BorisChiou:stylo/animation/transform/determinant_panic, r=birtles

Return Err(()) if determinant is not 1 or -1 while decomposing the 2d matrix

This error may happen in some cases, and we shouldn't panic in debug mode,
so let's return Err(()) for it to fall back to discrete animation.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [Bug 1393605](https://bugzilla.mozilla.org/show_bug.cgi?id=1393605).
- [X] These changes do not require tests because we just downgrade the panic to an Err result.

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

@@ -1692,8 +1692,8 @@ fn decompose_2d_matrix(matrix: &ComputedMatrix) -> Result<MatrixDecomposed3D, ()
     // |   0   0  0   1 |
     let (mut m11, mut m12) = (matrix.m11, matrix.m12);
     let (mut m21, mut m22) = (matrix.m21, matrix.m22);
+    // Check if this is a singular matrix.
     if m11 * m22 == m12 * m21 {
-        // singular matrix
         return Err(());
     }
 
@@ -1711,8 +1711,10 @@ fn decompose_2d_matrix(matrix: &ComputedMatrix) -> Result<MatrixDecomposed3D, ()
     shear_xy /= scale_y;
 
     let determinant = m11 * m22 - m12 * m21;
-    debug_assert!(0.99 < determinant.abs() && determinant.abs() < 1.01,
-                  "determinant should now be 1 or -1");
+    // Determinant should now be 1 or -1.
+    if 0.99 > determinant.abs() || determinant.abs() > 1.01 {
+        return Err(());
+    }
 
     if determinant < 0. {
         m11 = -m11;