[fuchsia][shader warmup] Fixed SkpWarmupTest

This test regressed due to flutter#23488
and this regression was silent due to flutter/flutter#78277

Credit to @gnoliyil for actually putting together the fix.

Author: freiling

shell/platform/fuchsia/flutter/tests/engine_unittests.cc

@@ -59,8 +59,9 @@ class EngineTest : public ::testing::Test {
     // otherwise we segfault creating the VulkanSurfaceProducer
     auto loop = fml::MessageLoopImpl::Create();
 
-    fuchsia::ui::scenic::SessionPtr session_ptr;
-    scenic::Session session(std::move(session_ptr));
+    context_ = sys::ComponentContext::CreateAndServeOutgoingDirectory();
+    scenic_ = context_->svc()->Connect<fuchsia::ui::scenic::Scenic>();
+    scenic::Session session(scenic_.get());
     surface_producer_ = std::make_unique<VulkanSurfaceProducer>(&session);
 
     Engine::WarmupSkps(&concurrent_task_runner_, &raster_task_runner_,
@@ -71,6 +72,9 @@ class EngineTest : public ::testing::Test {
   MockTaskRunner concurrent_task_runner_;
   MockTaskRunner raster_task_runner_;
   std::unique_ptr<VulkanSurfaceProducer> surface_producer_;
+
+  std::unique_ptr<sys::ComponentContext> context_;
+  fuchsia::ui::scenic::ScenicPtr scenic_;
 };
 
 TEST_F(EngineTest, SkpWarmup) {