Fix type annotation on [JSArray.addAll] and add a test.

tests/corelib/iterable_test.dart

Index: tests/corelib/iterable_test.dart
===================================================================
--- tests/corelib/iterable_test.dart	(revision 0)
+++ tests/corelib/iterable_test.dart	(revision 0)
@@ -0,0 +1,14 @@
+// Copyright (c) 2013, 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 dart2js where [List.addAll] was not typed
+// correctly.
+
+class MyIterable implements Iterable {
+  get iterator => [].iterator;
+}
+
+main() {
+  Expect.isTrue(([]..addAll(new MyIterable())).isEmpty);
+}