In Weston, clicking the window decoration of an Xwayland client gives us a wl_pointer.button event immediately followed by a wl_pointer.leave event. The leave event does not contain any button state information, so the button remains logically down in the DIX.
Once the pointer button is released, a wl_pointer.enter event is sent with the current button state (zero). This needs to trigger a ButtonRelease event but for that we need to ensure that the device is the same as the one we send ButtonPress events through.
Fixes a regression introduced in a4095162.