fuchsia: Fix renderer destructor

shell/platform/fuchsia/flutter/engine.cc

@@ -575,6 +575,20 @@ void Engine::Initialize(
 
 Engine::~Engine() {
   shell_.reset();
+
+  // Destroy rendering objects on the raster thread.
+  fml::AutoResetWaitableEvent view_embedder_latch;
+  thread_host_.raster_thread->GetTaskRunner()->PostTask(
+      fml::MakeCopyable([this, &view_embedder_latch]() mutable {
+        flatland_view_embedder_.reset();
+        external_view_embedder_.reset();
+        surface_producer_.reset();
+        flatland_connection_.reset();
+        session_connection_.reset();
+
+        view_embedder_latch.Signal();
+      }));
+  view_embedder_latch.Wait();
 }
 
 std::optional<uint32_t> Engine::GetEngineReturnCode() const {

shell/platform/fuchsia/flutter/engine.h

@@ -90,16 +90,14 @@ class Engine final {
   const std::string thread_label_;
   flutter::ThreadHost thread_host_;
 
-  std::optional<VulkanSurfaceProducer> surface_producer_;
-
-  // Gfx specific classes.
   fuchsia::ui::views::ViewToken view_token_;
-  std::shared_ptr<GfxSessionConnection> session_connection_;
-  std::shared_ptr<FuchsiaExternalViewEmbedder> external_view_embedder_;
-
-  // Flatland specific classes.
   fuchsia::ui::views::ViewCreationToken view_creation_token_;
-  std::shared_ptr<FlatlandConnection> flatland_connection_;
+  std::shared_ptr<GfxSessionConnection>
+      session_connection_;  // Must come before surface_producer_
+  std::shared_ptr<FlatlandConnection>
+      flatland_connection_;  // Must come before surface_producer_
+  std::optional<VulkanSurfaceProducer> surface_producer_;
+  std::shared_ptr<FuchsiaExternalViewEmbedder> external_view_embedder_;
   std::shared_ptr<FlatlandExternalViewEmbedder> flatland_view_embedder_;
 
   scenic::ViewRefPair view_ref_pair_;