Make bottom-left pixel of navbar clickable with mouse

The DeadZone is eating all clicks in the bottem-left pixel of the screen.
* Ignore mouse clicks for DeadZone, because it exists to compensate for
  low-precision finger input.
* Fix bug where "vertical" orientation consumes events along both the top
  and the left edge.
* Fix orientation for tablets so it correctly consumes events along the
  top edge.

Bug: 20091403
Change-Id: I8e97d894e380ece251f7920e5194c0dee4de0b43