Adds a View to the overlay. The bounds of the added view should be
relative to the host view. Any view added to the overlay should be
removed when it is no longer needed or no longer visible.
Views in the overlay are visual-only; they do not receive input
events and do not participate in focus traversal. Overlay views
are intended to be transient, such as might be needed by a temporary
animation effect.
If the view has a parent, the view will be removed from that parent
before being added to the overlay. Also, if that parent is attached
in the current view hierarchy, the view will be repositioned
such that it is in the same relative location inside the activity. For
example, if the view's current parent lies 100 pixels to the right
and 200 pixels down from the origin of the overlay's
host view, then the view will be offset by (100, 200).
mOverlayViewGroup.add(view);