title: How to force Angular 2 to re-check validator?
body: <p>I have a simple login form written in Angular 2 reactive (data-driven) template. It's working perfectly but when I refresh the page and browser fills e-mail+password (autocomplete), my form's valid property seems false.</p>
  
  <p>But when I press any key or click anywhere in my page while form is invalid, angular updates some states (I guess) and my form become valid.</p>
  
  <p>How can I trigger that state? How can I say angular "Hey, check my form again."? I can't trigger my own validation script because some validation messages are alerts. If I do this, when user open this page, he/she will see these alerts.</p>
  
  <p>I remember, I use trigger('input') trick to update ng-model.</p>