Previously the mouse position in the view was tracked using the
pointerPosition property. Scaling and relative mosue movements
were calculated in the view using screen properties stored in the
videoContext structure. Now when moving to iOSGraphicsManager all
that handling will be handled by the WindowedGraphicsManager,
which the iOSGraphicsManager inherit.
Rework the input code to send down pure x and y position values,
scaled according to the view content scale factor.
Remove code related to mouse movement that is no longer needed.
e0ae1a1d47