The default value for NullableString should be null (was "")

mojo/public/js/bindings/codec_unittests.js

Index: mojo/public/js/bindings/codec_unittests.js
diff --git a/mojo/public/js/bindings/codec_unittests.js b/mojo/public/js/bindings/codec_unittests.js
index 80f1402eef2ac0c7df9f346f1f80ba17fe7fddbe..0276db21bae8c00cfa9c745b776fd5f28d691f67 100644
--- a/mojo/public/js/bindings/codec_unittests.js
+++ b/mojo/public/js/bindings/codec_unittests.js
@@ -188,6 +188,7 @@ define([
       expect(result).toEqual(expectedResult);
     }
     encodeDecode(codec.String, "banana", "banana", 24);
+    encodeDecode(codec.NullableString, null, null, 8);
     encodeDecode(codec.Int8, -1, -1);
     encodeDecode(codec.Int8, 0xff, -1);
     encodeDecode(codec.Int16, -1, -1);