title: Angular ReactiveFrorm: Should setValue trigger ngModelChange
body: <p>I have the following code:</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;form [formGroup]="form" (ngSubmit)="register()"&gt;
      &lt;div&gt;
          &lt;input type="text" formControlName="username" (ngModelChange)="updateErrors('username')" /&gt;
      &lt;/div&gt;
  
      &lt;div&gt;
        &lt;button size="large" type="button" (click)="form.get('username').setValue('User')"&gt;Set username&lt;/button&gt;
      &lt;/div&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>When I click the "Set username" button the value of <code>username</code> changes but the <code>updateErrors</code> method is not called.</p>
  
  <p>Should it be? Maybe it should not but I do not understand something about <code>ngModelChange</code> event... (?)</p>