"track by" not working when returning new object in ng-controller function used in ng-repeat

Question

Can someone explain why this simple demo code always have the error: "[$rootScope:infdig] 10 $digest() iterations reached. Aborting!"

http://jsfiddle.net/bigbearzhu/Sx3Qq/

There is one scope function returning new object with same data every time:

$scope.items = function() {
    return [
        { id: 1 }
    ];
};

The track by item.id seems not working to stop the error.

Can't figure out how to get rid of the error. Drove me crazy for hours!