test: add core particle render layer validation

src/mbgl/renderer/layers/render_particle_validation_layer.hpp

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <mbgl/renderer/render_layer.hpp>
+#include <mbgl/style/layers/particle_validation_layer_impl.hpp>
+
+namespace mbgl {
+
+// VALIDATION ONLY: proves Core RenderLayer/frame-transform/repaint integration.
+class RenderParticleValidationLayer final : public RenderLayer {
+public:
+    explicit RenderParticleValidationLayer(Immutable<style::ParticleValidationLayer::Impl>);
+    ~RenderParticleValidationLayer() override;
+
+    void update(gfx::ShaderRegistry&,
+                gfx::Context&,
+                const TransformState&,
+                const std::shared_ptr<UpdateParameters>&,
+                const RenderTree&,
+                UniqueChangeRequestVec&) override;
+
+private:
+    void transition(const TransitionParameters&) override {}
+    void evaluate(const PropertyEvaluationParameters&) override;
+    bool hasTransition() const override { return false; }
+    bool hasCrossfade() const override { return false; }
+    bool needsRepaint() const override;
+    void prepare(const LayerPrepareParameters&) override {}
+};
+
+} // namespace mbgl