Remove unused private field.
Remove unused private field.

The usages were removed in cl/176030536.

PiperOrigin-RevId: 176439307

chalin/angular2,angulardart/angular,chalin/angular2,chalin/angular2,kevmoo/angular,matanlurey/angular,matanlurey/angular,angulardart/angular,kevmoo/angular,angulardart/angular,kevmoo/angular,matanlurey/angular