title: How to stay focus/active on button after click to open mat-menu in Angular Material?
body: <p>I have problem with focus in Angular Material. When I want open mat-menu, button after click is not actived or focused, and has default color. After closed mat-menu, button is again focused/activated. Where is the problem?</p>
  <p><strong>Example source:</strong></p>
  <p><a href="https://stackblitz.com/edit/angular-focus-after-click-to-open-mat-menu?file=src%2Fapp%2Fapp.component.html" rel="nofollow noreferrer">https://stackblitz.com/edit/angular-focus-after-click-to-open-mat-menu?file=src%2Fapp%2Fapp.component.html</a></p>
  <p>How can I resolve this problem?
  Thanks!</p>