Store the async-await compiled pub code directly in the repo.

sdk/lib/_internal/pub_generated/test/dart2js/minifies_in_release_mode_test.dart

Index: sdk/lib/_internal/pub_generated/test/dart2js/minifies_in_release_mode_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/dart2js/minifies_in_release_mode_test.dart b/sdk/lib/_internal/pub_generated/test/dart2js/minifies_in_release_mode_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..01014228d3e7f29b9ea64c30fcafe05298f59c53
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/test/dart2js/minifies_in_release_mode_test.dart
@@ -0,0 +1,18 @@
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import '../serve/utils.dart';
+main() {
+  initConfig();
+  integration("generates minified JS in release mode", () {
+    d.dir(
+        appPath,
+        [
+            d.appPubspec(),
+            d.dir(
+                "web",
+                [d.file("main.dart", "void main() => print('hello');")])]).create();
+    pubServe(args: ["--mode", "release"]);
+    requestShouldSucceed("main.dart.js", isMinifiedDart2JSOutput);
+    endPubServe();
+  });
+}