Check for duplicate library names

test/browser/runtime_tests.js

Index: test/browser/runtime_tests.js
diff --git a/test/browser/runtime_tests.js b/test/browser/runtime_tests.js
index e8d6ad944abad64bb7ad8193cb6acd71c67ca9b8..75472cfc07f1420b36527f0980e5be451264189b 100644
--- a/test/browser/runtime_tests.js
+++ b/test/browser/runtime_tests.js
@@ -3,6 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 var assert = chai.assert;
+var core = dart.import('dart/core.js');
+var collection = dart.import('dart/collection.js');
 
 suite('generic', () => {
   "use strict";