cleanup(forms): Change AbstractControl.valid to use == instead of identical.
cleanup(forms): Change AbstractControl.valid to use == instead of identical.

This is consistent with AbstractControl.pending, which already used ==.

PiperOrigin-RevId: 189804689

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