layout: Enable rendering of `conical-gradient` and `repeating-conical-gradient` (#31597)

This also ignores a clippy warning for a new function (and a similar
existing one), until this code can be refactored to use temporary Rust
strutures to carry display list building state.

There are a few new test failures here:

 - FAIL [expected PASS] /css/css-images/image-set/image-set-conic-gradient-rendering.html
 - FAIL [expected PASS] /css/css-images/image-set/image-set-repeating-conic-gradient-rendering.html

 These fail because Servo does not yet support `image-set()`.

 - FAIL [expected PASS] /css/filter-effects/filter-function/filter-function-conic-gradient.html
 - FAIL [expected PASS] /css/filter-effects/filter-function/filter-function-repeating-conic-gradient.html

 These fail because Servo does not support the very early filter effects
 specification.

 - FAIL [expected PASS] /html/canvas/element/manual/fill-and-stroke-styles/conic-gradient-rotation.html
 - FAIL [expected PASS] /html/canvas/element/manual/fill-and-stroke-styles/conic-gradient.html

 These fail because this change only adds support for CSS conical
 gradients. Another set of changes will be necessary to support this for
 Canvas.

1 files changed, 2 insertions, 2 deletions

diff --git a/components/layout/display_list/builder.rs b/components/layout/display_list/builder.rs
index 6d070f3d525..f85d5c3e0d7 100644
--- a/components/layout/display_list/builder.rs
+++ b/components/layout/display_list/builder.rs
@@ -1019,7 +1019,7 @@ impl Fragment {
                     };
                     DisplayItem::RadialGradient(CommonDisplayItem::with_data(base, item, stops))
                 },
-                Gradient::Conic { .. } => unimplemented!(),
+                Gradient::Conic { .. } => return,
             };
             state.add_display_item(display_item);
         });
@@ -1273,7 +1273,7 @@ impl Fragment {
                     stops = radial_stops;
                     NinePatchBorderSource::RadialGradient(wr_gradient)
                 },
-                Gradient::Conic { .. } => unimplemented!(),
+                Gradient::Conic { .. } => return None,
             },
             _ => return None,
         };