Support configuring dart2js from the pubspec.

sdk/lib/_internal/pub/test/transformer/dart2js/does_not_support_invalid_command_line_options_type_test.dart

Index: sdk/lib/_internal/pub/test/transformer/dart2js/does_not_support_invalid_command_line_options_type_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/dart2js/does_not_support_invalid_command_line_options_type_test.dart b/sdk/lib/_internal/pub/test/transformer/dart2js/does_not_support_invalid_command_line_options_type_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c13a5a28256f2f75e78812c11a2d37b181996357
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/transformer/dart2js/does_not_support_invalid_command_line_options_type_test.dart
@@ -0,0 +1,43 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library pub_tests;
+
+import 'package:scheduled_test/scheduled_test.dart';
+
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+import '../../serve/utils.dart';
+
+main() {
+  initConfig();
+
+  integration("doesn't support invalid commandLineOptions type", () {
+    d.dir(appPath, [
+      d.pubspec({
+        "name": "myapp",
+        "transformers": [{
+          "\$dart2js": {
+            "commandLineOptions": "foo",
+          }
+        }]
+      }),
+      d.dir("lib", [d.dir("src", [
+        d.file("transformer.dart", REWRITE_TRANSFORMER)
+      ])]),
+      d.dir("web", [d.file("main.dart", "void main() {}")])
+    ]).create();
+
+    createLockFile('myapp', pkg: ['barback']);
+
+    var server = pubServe();
+    expect(server.nextErrLine(), completion(equals('Build error:')));
+    expect(server.nextErrLine(), completion(equals(
+        'Transform Dart2JS on myapp|web/main.dart threw error: '
+            'FormatException: Invalid value for \$dart2js.commandLineOptions: '
+            '"foo" (expected list of strings).')));
+    requestShould404("main.dart.js");
+    endPubServe();
+  });
+}