Fix a bug in the container tracer, where the returned value of a closurized method was not traced c…

tests/language/list_tracer_return_from_tearoff_closure_test.dart

Index: tests/language/list_tracer_return_from_tearoff_closure_test.dart
===================================================================
--- tests/language/list_tracer_return_from_tearoff_closure_test.dart	(revision 0)
+++ tests/language/list_tracer_return_from_tearoff_closure_test.dart	(revision 0)
@@ -0,0 +1,20 @@
+// 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's list tracer, that used to not see a
+// returned value of a method can escape to places where that method
+// is closurized and invoked.
+
+var a = [42];
+
+foo() {
+  return a;
+}
+
+main() {
+  (foo)().clear();
+  if (a.length == 1) {
+    throw 'Test failed';
+  }
+}