Tests binary headers in Fetch.fulfillRequest.
Request to http://a.test/step1, type: Document
Request to http://a.test/step2?%D1%82%D0%B5%D1%81%D1%82, type: Document
Navigated to: http://a.test/step2?%D1%82%D0%B5%D1%81%D1%82
Request to http://a.test/subresource, type: XHR
Subresource headers: hétérogénéité, value