test: add core particle render layer validation

include/mbgl/layermanager/particle_validation_layer_factory.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <mbgl/layermanager/layer_factory.hpp>
+
+namespace mbgl {
+
+// VALIDATION ONLY: factory for the 30-01 Core RenderLayer experiment.
+class ParticleValidationLayerFactory final : public LayerFactory {
+public:
+    const style::LayerTypeInfo* getTypeInfo() const noexcept override;
+    std::unique_ptr<style::Layer> createLayer(const std::string&,
+                                              const style::conversion::Convertible&) noexcept override;
+    std::unique_ptr<RenderLayer> createRenderLayer(Immutable<style::Layer::Impl>) noexcept override;
+};
+
+} // namespace mbgl

include/mbgl/style/layers/particle_validation_layer.hpp

@@ -0,0 +1,32 @@
+#pragma once
+
+#include <mbgl/style/layer.hpp>
+
+namespace mbgl {
+namespace style {
+
+// VALIDATION ONLY: minimal source-less Core layer for 30-01 architecture validation.
+class ParticleValidationLayer final : public Layer {
+public:
+    explicit ParticleValidationLayer(const std::string& layerID);
+    ~ParticleValidationLayer() override;
+
+    bool isActive() const;
+    void setActive(bool);
+
+    class Impl;
+    const Impl& impl() const;
+    Mutable<Impl> mutableImpl() const;
+
+private:
+    explicit ParticleValidationLayer(Immutable<Impl>);
+
+    std::optional<conversion::Error> setPropertyInternal(const std::string&, const conversion::Convertible&) override;
+    StyleProperty getProperty(const std::string&) const override;
+    Value serialize() const override;
+    std::unique_ptr<Layer> cloneRef(const std::string& id) const override;
+    Mutable<Layer::Impl> mutableBaseImpl() const override;
+};
+
+} // namespace style
+} // namespace mbgl