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

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

Index: sdk/lib/_internal/pub_generated/test/dart2js/does_not_support_invalid_environment_type_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/dart2js/does_not_support_invalid_environment_type_test.dart b/sdk/lib/_internal/pub_generated/test/dart2js/does_not_support_invalid_environment_type_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..97c0b2a77d963f7c97077891251487a50dc75894
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/test/dart2js/does_not_support_invalid_environment_type_test.dart
@@ -0,0 +1,24 @@
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import '../serve/utils.dart';
+main() {
+  initConfig();
+  integration("doesn't support invalid environment type", () {
+    d.dir(appPath, [d.pubspec({
+        "name": "myapp",
+        "transformers": [{
+            "\$dart2js": {
+              "environment": "foo"
+            }
+          }]
+      }), d.dir("web", [d.file("main.dart", "void main() {}")])]).create();
+    var server = pubServe();
+    requestShould404("main.dart.js");
+    server.stderr.expect(
+        emitsLines(
+            'Build error:\n' 'Transform Dart2JS on myapp|web/main.dart threw error: '
+                'Invalid value for \$dart2js.environment: "foo" '
+                '(expected map from strings to strings).'));
+    endPubServe();
+  });
+}