OpenGL: Implement Fencing backend.

src/video_core/gpu_thread.cpp

@@ -37,6 +37,8 @@ static void RunThread(VideoCore::RendererBase& renderer, Core::Frontend::Graphic
             dma_pusher.DispatchCalls();
         } else if (const auto data = std::get_if<SwapBuffersCommand>(&next.data)) {
             renderer.SwapBuffers(data->framebuffer ? &*data->framebuffer : nullptr);
+        } else if (const auto data = std::get_if<OnCommandListEndCommand>(&next.data)) {
+            renderer.Rasterizer().ReleaseFences();
         } else if (const auto data = std::get_if<FlushRegionCommand>(&next.data)) {
             renderer.Rasterizer().FlushRegion(data->addr, data->size);
         } else if (const auto data = std::get_if<InvalidateRegionCommand>(&next.data)) {
@@ -95,6 +97,10 @@ void ThreadManager::WaitIdle() const {
     }
 }
 
+void ThreadManager::OnCommandListEnd() {
+    PushCommand(OnCommandListEndCommand());
+}
+
 u64 ThreadManager::PushCommand(CommandData&& command_data) {
     const u64 fence{++state.last_fence};
     state.queue.Push(CommandDataContainer(std::move(command_data), fence));