Add test for issue fixed in r3707.

tests/language/src/TopLevelPrefixedDeclarationTest.dart

Index: tests/language/src/TopLevelPrefixedDeclarationTest.dart
===================================================================
--- tests/language/src/TopLevelPrefixedDeclarationTest.dart	(revision 0)
+++ tests/language/src/TopLevelPrefixedDeclarationTest.dart	(revision 0)
@@ -0,0 +1,20 @@
+// Copyright (c) 2012, 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.
+//
+// Dart test for top level declarations involving an imported type.
+
+#library("main");
+#import("library11.dart", prefix : "lib11");
+
+lib11.Library11 variable = null;
+
+lib11.Library11 function() => null;
+
+lib11.Library11 get getter() => null;
+
+main() {
+  Expect.isTrue(variable == null);
+  Expect.isTrue(function() == null);
+  Expect.isTrue(getter == null);
+}