SurfaceFlinger Input: Correct screen magnification.

We need to pass the computed scaling factors through SurfaceFlinger
as well as appropriately scaling the touchable region. We also need
to be careful as to which axes we scale. In the past screen magnification
has not lead to scaling of the TOUCH_MAJOR/MINOR axes, whereas whole-screen
display compatibility scaling has. We preserve this behavior by differentiating
between the global scale and a scale on any particular window. The window scale
works like the global scale used to and the global scale is only used for additional
scaling of the MAJOR/MINOR axes.

Bug: 80101428
Bug: 113136004
Bug: 111440400
Change-Id: I97d809826f86b452f28443cb1046e8bfef1bbf9d