[Impeller] Fix scene build

display_list/display_list_color_source.h

@@ -702,8 +702,6 @@ class DlSceneColorSource final : public DlColorSource {
 
   impeller::Matrix camera_matrix() const { return camera_matrix_; }
 
-  sk_sp<SkShader> skia_object() const override { return nullptr; }
-
  protected:
   bool equals_(DlColorSource const& other) const override {
     FML_DCHECK(other.type() == DlColorSourceType::kScene);

display_list/skia/dl_sk_conversions.cc

@@ -106,6 +106,11 @@ sk_sp<SkShader> ToSk(const DlColorSource* source) {
       return runtime_effect->skia_runtime_effect()->makeShader(
           sk_uniform_data, sk_samplers.data(), sk_samplers.size());
     }
+#ifdef IMPELLER_ENABLE_3D
+    case DlColorSourceType::kScene:
+      // Impeller Scene is not supported for Skia.
+      return nullptr;
+#endif
   }
 }