Tests the navigation request related events are available in the DevTools

-----------------
Loading an iframe.
onRequestStarted:
  url: http://127.0.0.1:8000/devtools/service-workers/resources/navigation-preload-scope.php
onResponseReceived:
  statusCode: 200
  timing available: true
  requestHeaders['Service-Worker-Navigation-Preload']: hello
onRequestFinished:
The iframe loaded.
-----------------
Loading another iframe.
onRequestStarted:
  url: http://127.0.0.1:8000/devtools/service-workers/resources/navigation-preload-scope.php?BrokenChunked
onResponseReceived:
  statusCode: 200
  timing available: true
  requestHeaders['Service-Worker-Navigation-Preload']: hello
onRequestFinished:
  localizedFailDescription: net::ERR_INVALID_CHUNKED_ENCODING
The iframe loaded.
-----------------
Loading another iframe.
onRequestStarted:
  url: http://127.0.0.1:8000/devtools/service-workers/resources/navigation-preload-scope.php?Redirect
onResponseReceived:
  statusCode: 302
  timing available: true
  requestHeaders['Service-Worker-Navigation-Preload']: hello
onRequestFinished:
The iframe loaded.
-----------------
Done