Fix ViewTreeObserverTest in Landscape Orientation

Bug 5679517

The content view had a LinearLayout with horizontal orientation,
so the button ended up near the navigation bar which rejected
the simulated pointer event. Change the layout to use vertical
orientation.

The changes in ViewTreeObserverTest are just to remove warnings
and get rid of the testing annotations.

Change-Id: Ibd062336ef1285305fc8238a5a78190a3ec57656