pepper: View damage processing

pepper: View damage processing

Damage processing algorithm.

1. inflict damage for current visible area of a view when geometry or z-order
   change. Mark those views as "need_damage" so that damages for updated
   visible regions are getting inflicted.

2. Build a list of views sorted in z-order.

3. Do following things while traversing the view list from front to back

    a. update view geometry
    b. calculate visible region of the view : visible = bounding - opaque
    c. inflict damage for visible region of the view if marked as "need_damage"
    d. inflict damage for surface damage set by the client
    e. accumulate view's opaque region on the global opaque region

Now we have total damage region in compositor->damage_region.

Change-Id: I06c7098bb7edc954172177ee36442800d2b3ce26