@zqzhang on w3c-test.org, /resources/WebIDLParser.js is a symlink to /resources/webidl2/lib/webidl2.js. And the wptserve code re-routes /resources/WebIDLParser.js requests to /resources/webidl2/lib/webidl2.js

That said, I'm not clear why for new tests we're not just switching over to /resources/webidl2/lib/webidl2.js There are not even that many existing tests that use /resources/WebIDLParser.js (so even chaning all the existing tests to use /resources/webidl2/lib/webidl2.js would not be a lot of work).