QScroller::grabGesture causes delay in handling tap events and disables double-tap

Reproducer attached.

Steps to reproduce the issue :

1. Prepare A touch-display Windows device or an external touch-display.

2. Run the attached reproducer.

3. Tap the "Input text" button several times, then 'A' will be displayed in the QLineEdit every time you click. Try double-tap on the "Double tap" label to check it responds. 

4. Tap the "grabGesture" button to enable QScroller::grabGesture.

5. Try the same as step 3. You will see some delay in displaying 'A', and you will find double-tap on the "Double tap" label is not detected. 

6. Tap the "ungrabGesture" to disable grabGesture. After that, the delay observed in step 5 will disappear and the double-ctap will be detected again.

How can I avoid the delay and enable double-tap again while grabGesture enabled?