It seems that is not possible to have a DragHandler in a parent item and handle the following scenario:

1. One DragHandler in parent Item "Rect1"
2. "Rect1" contains both a ListView ("ListView1") and a
   Button ("Button1")
3. The user would like to being able to scroll "ListView1" without
   triggering "Rect1" DragHandler but being able to drag
   "Rect1" when drag is done over "Button1"

In other words we would like to have DragHandler that win over Buttons but lose with ListViews or child DragHandlers.

The funny or absurd thing is that using a TapHandler doesn't causes the same effects of a Button.
Where a Button seems to take the grab a TapHandler doesn't prevent the parent DragHandler to start the drag gesture.
Maybe the Button should be ported to TapHandlers? or maybe the DragHandler grabPermissions policies must be increased with ListViews and Flickable items.

IMPORTANT: for testing this bug report you need a device that sends touch events. With mouse is not reproducible