Support passing configuration data to a transformer plugin.

sdk/lib/_internal/pub/test/serve/fails_to_load_a_pubspec_with_reserved_transformer_config_test.dart

Index: sdk/lib/_internal/pub/test/serve/fails_to_load_a_pubspec_with_reserved_transformer_config_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart b/sdk/lib/_internal/pub/test/serve/fails_to_load_a_pubspec_with_reserved_transformer_config_test.dart
similarity index 57%
copy from sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart
copy to sdk/lib/_internal/pub/test/serve/fails_to_load_a_pubspec_with_reserved_transformer_config_test.dart
index b9b3073dd622a659a051c7039842035dd98f1f18..5ba03d8353992149139f163dcd1ecf6cc99b0c02 100644
--- a/sdk/lib/_internal/pub/test/serve/fails_to_load_a_transform_with_a_syntax_error_test.dart
+++ b/sdk/lib/_internal/pub/test/serve/fails_to_load_a_pubspec_with_reserved_transformer_config_test.dart
@@ -8,29 +8,29 @@ import 'package:scheduled_test/scheduled_test.dart';
 
 import '../descriptor.dart' as d;
 import '../test_pub.dart';
+import 'utils.dart';
 
 main() {
   initConfig();
 
-  // A syntax error will cause the analyzer to fail to parse the transformer
-  // when attempting to rewrite its imports.
-  integration("fails to load a transform with a syntax error", () {
+  integration("fails to load a pubspec with reserved transformer config", () {
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
-        "transformers": ["myapp/src/transformer"]
+        "transformers": [{"myapp/src/transformer": {'include': 'something'}}]
       }),
       d.dir("lib", [d.dir("src", [
-        d.file("transformer.dart", "syntax error")
+        d.file("transformer.dart", REWRITE_TRANSFORMER)
       ])])
     ]).create();
 
     createLockFile('myapp', pkg: ['barback']);
 
     var pub = startPub(args: ['serve', '--port=0']);
-    expect(pub.nextErrLine(), completion(startsWith('Error on line')));
+    expect(pub.nextErrLine(), completion(startsWith('Could not parse ')));
+    expect(pub.nextErrLine(), completion(equals('Configuration for '
+        'transformer myapp/src/transformer may not include reserved key '
+        '"include".')));
     pub.shouldExit(1);
-    expect(pub.remainingStderr(),
-        completion(isNot(contains('This is an unexpected error'))));
   });
 }