How do I get Geolocation API to work in Dartium?

I'm trying to test in Dartium browser using the Geolocation API. In particular I try doing the following

window.navigator
  .geolocation.getCurrentPosition()
    ..then((pos) {

      window.alert(pos.toString());
    })
    ..catchError((PositionError error) {
      window.alert("Error code: ${error.code}, Error message: ${error.message}");
    })
    ..whenComplete(() => window.alert("complete"))
    ;

Ignoring the fact I'm using window.alert here, All I get is an error with the following message "Error code: 2, Error message: Network location provider at 'https://www.googleapis.com/' : Returned error code 400."

However the same code works in Google Chrome when I use "pub serve". It also works with Firefox. How do I overcome this error, and get it to work in Dartium? Is it even possible?

UPDATE

I took a look at the 403 bug and tried using the fix specified on this page http://www.chromium.org/developers/how-tos/api-keys, and when I first tried this, I got my credentials and setting wrong, I was getting a 403 error, but once that was resolved, and all the APIs enabled, plus the environment settings of

GOOGLE_API_KEY
GOOGLE_DEFAULT_CLIENT_ID
GOOGLE_DEFAULT_CLIENT_SECRET

I was back to "Network location provider at 'https://www.googleapis.com/' : Returned error code 400.", so I conclude it isn't the same issue. Though if someone can prove me wrong, I'd be happy.