Forms: cyclic DI dependency when component is both valueAccessor and validator #4253

@Component(
    bindings: const [
      const Binding(NG_VALIDATORS, toAlias: MyComponent, multi: true)
    ])
class MyComponent {
  MyComponent(@Self() NgControl cd) {
    cd.valueAccessor = this;
  }
}

@Injectable()
class DeferredValidator {
  Function delegate;

  call(NgControl control) {
    return this.delegate(control);
  }
}

@Component(
    bindings: const [
      DeferredValidator,
      const Binding(NG_VALIDATORS, toAlias: DeferredValidator, multi: true)
    ])
class MyComponent {
  MyComponent(@Self() NgControl cd, DeferredValidator dv) {
    cd.valueAccessor = this;
    dv.delegate = this;
  }
}