Just for clarifications:
We use `interpolateFn.$$invoke(listener)` so we just interpolate [once](https://github.com/rodyhaddad/angular.js/blob/dart-interpolation-optimization/src/ng/compile.js#L1797) and reuse the same instance for multiple invocations of `link`. This couldn't be done if we were to use dart's [`.setter`](https://github.com/angular/angular.dart/blob/master/lib/core_dom/ng_mustache.dart#L38-L42) property