Implement pushColorFilter in CanvasKit

lib/web_ui/lib/src/engine/canvaskit/layer.dart

@@ -480,8 +480,8 @@ class PhysicalShapeLayer extends ContainerLayer
     assert(needsPainting);
 
     if (_elevation != 0) {
-      drawShadow(paintContext.leafNodesCanvas!, _path, _shadowColor!, _elevation,
-          _color.alpha != 0xff);
+      drawShadow(paintContext.leafNodesCanvas!, _path, _shadowColor!,
+          _elevation, _color.alpha != 0xff);
     }
 
     final ui.Paint paint = ui.Paint()..color = _color;
@@ -528,6 +528,25 @@ class PhysicalShapeLayer extends ContainerLayer
   }
 }
 
+/// A layer which contains a [ui.ColorFilter].
+class ColorFilterLayer extends ContainerLayer {
+  ColorFilterLayer(this.filter);
+
+  final ui.ColorFilter filter;
+
+  @override
+  void paint(PaintContext paintContext) {
+    assert(needsPainting);
+
+    CkPaint paint = CkPaint();
+    paint.colorFilter = filter;
+
+    paintContext.internalNodesCanvas.saveLayer(paintBounds, paint);
+    paintChildren(paintContext);
+    paintContext.internalNodesCanvas.restore();
+  }
+}
+
 /// A layer which renders a platform view (an HTML element in this case).
 class PlatformViewLayer extends Layer {
   PlatformViewLayer(this.viewId, this.offset, this.width, this.height);

lib/web_ui/lib/src/engine/canvaskit/layer_scene_builder.dart

@@ -138,12 +138,13 @@ class LayerSceneBuilder implements ui.SceneBuilder {
   }
 
   @override
-  ui.ColorFilterEngineLayer pushColorFilter(
+  ui.ColorFilterEngineLayer? pushColorFilter(
     ui.ColorFilter filter, {
     ui.ColorFilterEngineLayer? oldLayer,
   }) {
     assert(filter != null); // ignore: unnecessary_null_comparison
-    throw UnimplementedError();
+    pushLayer(ColorFilterLayer(filter));
+    return null;
   }
 
   ui.ImageFilterEngineLayer? pushImageFilter(

lib/web_ui/test/canvaskit/scene_test.dart

@@ -49,6 +49,17 @@ void testMain() {
       final ui.Image sceneImage = await scene.toImage(100, 100);
       expect(sceneImage, isA<CkImage>());
     });
-  // TODO: https://github.com/flutter/flutter/issues/60040
+
+    test('pushColorFilter does not throw', () async {
+      final ui.SceneBuilder builder = ui.SceneBuilder();
+      expect(builder, isA<LayerSceneBuilder>());
+
+      builder.pushOffset(0, 0);
+      builder.pushColorFilter(ui.ColorFilter.srgbToLinearGamma());
+
+      final ui.Scene scene = builder.build();
+      expect(scene, isNotNull);
+    });
+    // TODO: https://github.com/flutter/flutter/issues/60040
   }, skip: isIosSafari);
 }