cdkDragStartDelay behavior has changed in version 8.1.0

It seems that the behavior of drag start delay has been changed between Angular CDK versions 8.0.0 and 8.1.0. I think this is a breaking change since it completely changes the way users interact with draggable items. I am not sure if the current behavior is really intended.

#### Reproduction

8.0.0: https://stackblitz.com/edit/angular-cdkdragstartdelay-80
8.1.0: https://stackblitz.com/edit/angular-cdkdragstartdelay-81

Steps to reproduce:
1. Click on any item.
2. Try to drag it as soon as possible.


#### Expected Behavior

In the previous version it did not matter if the mouse was clicked or immediately moved. The dragging started anyway after the specified delay.

#### Actual Behavior

In the current version the item is not being dragged when you move the mouse immediately after the initial click. It only works if you stay at the click position for the specified delay time and then move the mouse.

#### Environment

- Angular: 8.0.0+
- CDK/Material: 8.1.0+
- Browser(s): Google Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Fedora Linux 29

Commencez par comparer les deux reproductions StackBlitz liées pour Angular CDK 8.0.0 et 8.1.0, en vous concentrant sur cdkDragStartDelay et la séquence consistant à cliquer puis à déplacer immédiatement. Suivez l’implémentation du glisser-déposer utilisée par les reproductions et vérifiez le comportement par rapport aux résultats attendus et réels indiqués.

Rédigé par le modèle d'indexation à partir du texte de l'issue.