Fix bug in ClassElement.lookupSelector: by returning an abstract method, we were not returning the …

tests/language/super_abstract_method_test.dart

Index: tests/language/super_abstract_method_test.dart
===================================================================
--- tests/language/super_abstract_method_test.dart	(revision 0)
+++ tests/language/super_abstract_method_test.dart	(revision 0)
@@ -0,0 +1,25 @@
+// 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.
+
+// Test that a method overridden by an abstract method is called at
+// runtime.
+
+import "package:expect/expect.dart";
+
+class Base {
+  foo() => 42;
+}
+
+abstract class A extends Base {
+  foo();
+}
+
+class B extends A {
+  testSuperCall() => super.foo();
+}
+
+main() {
+  Expect.equals(42, new B().foo());
+  Expect.equals(42, new B().testSuperCall());
+}