[default] manage backendscope in renderer frontend

platform/default/mbgl/gl/headless_backend.cpp

@@ -12,7 +12,7 @@ namespace mbgl {
 HeadlessBackend::HeadlessBackend() = default;
 
 HeadlessBackend::~HeadlessBackend() {
-    BackendScope guard { *this, getScopeType() };
+    BackendScope guard { *this };
     context.reset();
 }
 

platform/default/mbgl/renderer/async_renderer_frontend.cpp

@@ -1,13 +1,16 @@
 #include "async_renderer_frontend.hpp"
+
+#include <mbgl/renderer/backend_scope.hpp>
 #include <mbgl/renderer/renderer.hpp>
 
 namespace mbgl {
 
-AsyncRendererFrontend::AsyncRendererFrontend(std::unique_ptr<Renderer> renderer_, View& view_)
+AsyncRendererFrontend::AsyncRendererFrontend(std::unique_ptr<Renderer> renderer_, RendererBackend& backend, View& view_)
     : renderer(std::move(renderer_))
     , view(view_)
-    , asyncInvalidate([this] {
+    , asyncInvalidate([&] {
         if (renderer && updateParameters) {
+            BackendScope guard { backend };
             renderer->render(view, *updateParameters);
         }
     }) {

platform/default/mbgl/renderer/async_renderer_frontend.hpp

@@ -10,11 +10,12 @@
 namespace mbgl {
     
 class Renderer;
+class RendererBackend;
 
 // Default implementation for RendererFrontend
 class AsyncRendererFrontend : public mbgl::RendererFrontend {
 public:
-    AsyncRendererFrontend(std::unique_ptr<Renderer>, View&);
+    AsyncRendererFrontend(std::unique_ptr<Renderer>, RendererBackend&, View&);
     ~AsyncRendererFrontend() override;
 
     void reset() override;