title: Change event triggered too quick from the mat-slider with Angular 7
body: <p>The problem appeared after upgrading to angular 7. If you click on the slider without releasing the click (mouseup), it still trigger and emit to the change event. How can I ignore that event? Sometime people will start dragging a few pixel beside the real center of the label and I want to prevent the change event at that moment.</p>
  
  <pre><code> &lt;mat-slider
      class="example-margin"
      [disabled]="disabled"
      [invert]="invert"
      [max]="max"
      [min]="min"
      [step]="step"
      (change)="change($event)"
      [thumbLabel]="thumbLabel"
      [tickInterval]="tickInterval"
      [(ngModel)]="value"
      [vertical]="vertical"&gt;
  &lt;/mat-slider&gt;
  
  public change($event) {
      alert('trace');
      console.log($event);
      // need a way to ignore the first trigger if the slider is still being dragged
    }
  </code></pre>