google_auth and Dart 2

i am trying to create a webapp that uses google apis and needs to authenticate the user with the google auth api. so i got the example at

https://github.com/dart-lang/googleapis_examples/tree/master/drive_search_web

and tried to run it. i use webstorm and dart 2.0.0-dev.68.0. the webpage can be called, but the code never runs into the then-part of authorizedClient in main-function and also gives me no popup window where i can login to google services.

it seems that the function flow.clientViaUserConsent in authorizedClient doesn't do anything.

is the support of google_auth in dart 2 broken or is the example on github not up to date with the current dart development?