title: Angular form control disabled binding not working
body: <p>I have a form control that I disable when the page loads. When  the user clicks a button the forms should become enabled for editing. However when I toggle the property that disabled the control nothing happens.</p>
  
  <p><strong>Template</strong></p>
  
  <pre><code>&lt;form [formGroup]='accountForm'&gt;
    &lt;md-input-container&gt;
      &lt;input mdInput formControlName='name' /&gt;
    &lt;/md-input-container&gt;
    &lt;button (click)='isEditing = !isEditing'&gt;Edit&lt;/button&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p><strong>Component</strong></p>
  
  <pre><code>export class AccountComponent {
    private accountForm: FormGroup;
    private isEditing = false;
    private name: FormControl = new FormControl({ value: '', disabled: !isEditing; 
  
    constructor(
      formBuilder: FormBuilder
    ) {
      this.accountForm = formBuilder.group({
        'name': this.name
      });
    });
  }
  </code></pre>