Revert "Compile embedder unit test Dart to kernel (#7227)" (flutter/engine#7230)

This reverts commit 4e4fb4608d.

This broke dynamic release mode builds of
//flutter/runtime:runtime_fixtures_kernel (likely all product-mode
builds).

engine/src/flutter/runtime/fixtures/simple_main.dart

@@ -2,6 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-void main() {
+void simple_main() {
   print("Hello");
 }

engine/src/flutter/shell/platform/embedder/fixtures/simple_main.dart

@@ -1 +1 @@
-void main() {}
+void main() {}

engine/src/flutter/shell/platform/embedder/tests/embedder_unittests.cc

@@ -22,14 +22,17 @@ TEST(EmbedderTest, CanLaunchAndShutdownWithValidProjectArgs) {
     return false;
   };
 
+  std::string main =
+      std::string(testing::GetFixturesPath()) + "/simple_main.dart";
+
   FlutterRendererConfig config = {};
   config.type = FlutterRendererType::kSoftware;
   config.software = renderer;
 
   FlutterProjectArgs args = {};
   args.struct_size = sizeof(FlutterProjectArgs);
-  args.assets_path = testing::GetFixturesPath();
-  args.main_path = "";
+  args.assets_path = "";
+  args.main_path = main.c_str();
   args.packages_path = "";
 
   FlutterEngine engine = nullptr;

engine/src/flutter/testing/testing.gni

@@ -2,21 +2,18 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//third_party/dart/build/dart/dart_action.gni")
-
-# Builds test fixtures for a unit test.
-#
-# Generates a directory structure containing an assets directory and the Dart
-# code to execute compiled to kernel, emitted to assets/kernel_blob.bin.
 template("test_fixtures") {
   testonly = true
 
   assert(defined(invoker.fixtures), "Test fixtures must be specified.")
 
-  fixtures_location = "$target_gen_dir/$target_name/assets"
-  fixtures_location_file = "$target_gen_dir/$target_name/test_fixtures_location.cc"
-
   fixtures_name_target_name = target_name + "_gen_fixtures_name"
+  fixtures_source_set_target_name = target_name + "_gen_fixtures_source_set"
+  fixtures_copy_target_name = target_name + "_copy_fixtures"
+
+  fixtures_location = "$target_gen_dir/fixtures"
+  fixtures_location_file = "$target_gen_dir/test_fixtures_location.cc"
+
   action(fixtures_name_target_name) {
     script = "$flutter_root/testing/build/gen_fixtures_location_symbol.py"
 
@@ -32,9 +29,7 @@ template("test_fixtures") {
     ]
   }
 
-  fixtures_source_set_target_name = target_name + "_gen_fixtures_source_set"
   source_set(fixtures_source_set_target_name) {
-    testonly = true
     sources = [
       fixtures_location_file,
     ]
@@ -44,33 +39,16 @@ template("test_fixtures") {
     ]
   }
 
-  fixtures_kernel_target_name = target_name + "_kernel"
-  prebuilt_dart_action(fixtures_kernel_target_name) {
-    testonly = true
-    script = "$root_out_dir/frontend_server.dart.snapshot"
-
-    fixture_paths = []
-    foreach(fixture, invoker.fixtures) {
-      fixture_paths += [ rebase_path(fixture) ]
-    }
-    inputs = fixture_paths
-    outputs = ["$fixtures_location/kernel_blob.bin"]
-
-    args = [
-      "--sdk-root", rebase_path("$root_out_dir/flutter_patched_sdk"),
-      "--strong",
-      "--target", "flutter",
-      "--output-dill", rebase_path("$fixtures_location/kernel_blob.bin"),
-    ] + fixture_paths
-    deps = [
-      "//third_party/dart/utils/kernel-service:frontend_server"
+  copy(fixtures_copy_target_name) {
+    sources = invoker.fixtures
+    outputs = [
+      "$fixtures_location/{{source_file_part}}",
     ]
   }
 
   group(target_name) {
-    testonly = true
     deps = [
-      ":$fixtures_kernel_target_name",
+      ":$fixtures_copy_target_name",
       ":$fixtures_source_set_target_name",
     ]
   }