Fix handling of async patches.

tests/isolate/resolve_package_uri_test.dart

Index: tests/isolate/resolve_package_uri_test.dart
diff --git a/tests/isolate/resolve_package_uri_test.dart b/tests/isolate/resolve_package_uri_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..7aa387a9cb64c17b6c5a8b099e8df0f19f5b74f8
--- /dev/null
+++ b/tests/isolate/resolve_package_uri_test.dart
@@ -0,0 +1,14 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS 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.
+
+// Regression test for faulty encoding of `Isolate.resolvePackageUri` by
+// dart2js.
+
+import 'dart:async';
+import 'dart:isolate';
+
+main() {
+  Future<Uri> uri = Isolate.resolvePackageUri(Uri.parse('memory:main.dart'));
+  print(uri);
+}