When a stylus supports hover and when we lift the stylus Chrome sends a touchend message to Blink. Since Blink assumes touchend means the end of the sequence for the pointer it also sends the leave/out event after pointerup similar to touch.
However, when pen supports hover although it should send a pointerup but it should not send the leave until the pen leaves the range of the digitizer.
We need to probably look at is_pointer_inrange_param in WM_POINTERUP and expose this flag to Blink so it can make a decision whether to send the leave/out events after up.

https://msdn.microsoft.com/en-us/library/windows/desktop/hh454928(v=vs.85).aspx