Use selectors instead of names to know if a call site returns the element of a list. This fixes the…

tests/language/list_tracer_call_last_test.dart

Index: tests/language/list_tracer_call_last_test.dart
===================================================================
--- tests/language/list_tracer_call_last_test.dart	(revision 0)
+++ tests/language/list_tracer_call_last_test.dart	(revision 0)
@@ -0,0 +1,13 @@
+// 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.
+
+// dart2js used to fail this test, by inferring that `a.last()`
+// returns the element type of the `a` list.
+
+main() {
+  var a = [() => 123];
+  if (a.last() is! num) {
+    throw 'Test failed';
+  }
+}