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.

```
 <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">
</mat-slider>

public change($event) {
    alert('trace');
    console.log($event);
    // need a way to ignore the first trigger if the slider is still being dragged
  }

```