Verify that import prefixes don't shadow exports.

tests/language/export_not_shadowed_by_prefix_test.dart

 // Copyright (c) 2016, 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.
 
+// Verify that import prefixes within an imported library don't shadow
+// names re-exported by that library.
+
 import "package:expect/expect.dart";
-
-class A<T> {}
-
-class C<T> {
-  a() {
-    return () => new A<T>();
-  }
-}
+import "export_not_shadowed_by_prefix_helper.dart";
 
 main() {
-  Expect.isTrue(new C<int>().a()() is A<int>);
-  Expect.isFalse(new C<int>().a()() is A<String>);
+  f();
+  Expect.isTrue(f_called);
 }