Dart transformer ChangeDetectors do not have IDs

When running WTF in Dart with transformers all ChangeDetector ids are null. The issue is [here](https://github.com/angular/angular/blob/d191ec4c333ffcbbc8c1a85dfd78d96bfffeffd1/modules/angular2/src/change_detection/abstract_change_detector.ts#L89) the `this.id` is null, it seems that `id`s are not generated in transformer mode. This makes it hard to do debugging.
