third_party/web_platform_tests/WebIDL/valid/idl/treatasnull.widl

// Extracted from http://dev.w3.org/2006/webapi/WebIDL/ on 2011-05-06
interface Dog {
  attribute DOMString name;
  attribute DOMString owner;

  boolean isMemberOfBreed([TreatNullAs=EmptyString] DOMString breedName);
};