Support loading transformer plugins from pub.

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

Index: sdk/lib/_internal/pub/test/serve/does_not_run_a_transform_on_an_input_in_another_package_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/does_not_run_a_transform_on_an_input_in_another_package_test.dart b/sdk/lib/_internal/pub/test/serve/does_not_run_a_transform_on_an_input_in_another_package_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3a39dd3bf2931a24d0f9892ea2765b9a8c93fc17
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/serve/does_not_run_a_transform_on_an_input_in_another_package_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 '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+
+main() {
+  initConfig();
+  integration("does not run a transform on an input in another package", () {
+    d.dir("foo", [
+      d.pubspec({
+        "name": "foo",
+        "version": "0.0.1",
+        "transformers": ["foo/transformer"]
+      }),
+      d.dir("lib", [
+        d.file("transformer.dart", REWRITE_TRANSFORMER)
+      ]),
+      d.dir("asset", [
+        d.file("foo.txt", "foo")
+      ])
+    ]).create();
+
+    d.dir(appPath, [
+      d.appPubspec({"foo": {"path": "../foo"}}),
+      d.dir("asset", [
+        d.file("bar.txt", "bar")
+      ])
+    ]).create();
+
+    createLockFile('myapp', {
+      'foo': '../foo'
+    }, pkg: ['barback']);
+
+    startPubServe();
+    requestShould404("assets/myapp/bar.out");
+    endPubServe();
+  });
+}